My top ten favorite anime ending songs in no particular order and not complete by any means. I went more for a survey of good anime ending themes out there that might not always be the best known (or may be very popular already.) I think I cover a wide range of anime between shoujo, shounen, jousei and mecha.
1. I love it when the first chords of the ending song kick into the end of the anime episode. The quintessential example of this of Fushigi Yuugi's ending "Tokimeki no Doukousen," especially with the ending of the first episode which gave me the feeling, ah this anime is going to be epic. The Yuu Watase manga illustration at the end was beautiful as well. Note: I have not watched the anime nor read the manga in its entirety and still plan to one day.
2. Full Metal Alchemist is noted for its great music, and if I could, I would include all the songs in my list. If had to pick my top (and it's a real hard choice), I would pick FMA's second ending theme Yellow Generation's "Tobira no Mukou E" because I love the way the beginning of the song kicks in at the end of the episode, which gives me a tingling sense of anticipation. I didn't really fall for FMA until the mid-teen episodes, and then rapidly, before I knew it, I was hooked. Oddly enough, Crystal Kay's "Motherland" is probably overall the crowd's least favorite ED, but it's the most re-listenable one and is a constant on my playlist, more so than most other songs. FMA did the progression of ending themes very well from the angsty and slightly bitter-toned Nana Kitade song "Kesenai Tsumi" or "Inerasable Sin" (I love the acoustic raw-breath version even more), the frustration and desperation felt in Tobira with it's opening lyrics, "The two of us are screaming, even now" (paired with music that is somewhat forward-looking and ends with a sense of hope), the nostalgic "Motherland" and finally the wistful Sowelu's "I Will." I found the last image in the ED 2 video very poignant, when the snowflake melts from the warmth of Ed's real hand and doesn't in his metal arm.
3. Honey and Clover 1st ending Sunohair's "Waltz" just pairs one of my favorite ending songs with my favorite anime. One of Honey and Clover's winning points (besides great character, plot, comedy drama and animation) is music, since it was named after to albums. Especially since the first half of season 1is so much more light-hearted than the rest of the series, this ending just embodies hope and youth. (And yes, I love it when the first chords of the ending kicks in at the end.)
4. Detective Conan Ending 17 - "Overture" by Inaba Koshi (of B'z). Yes, this is the song I really fell in love with B'z, who have done other Detective Conan related music. There are songs that the first time you hear it, it sense shivers down your spine. It was once said that Inaba Koshi's voice is one of Japan's national treasures, and I whole-heartedly agree. Matsumoto Tak and Inaba Koshi are really a dream combination. Overall, Detective Conan boasts an awesome OP and ED collection--sometimes I like the animations of the OP and ED even better than the story because they're angsty and more romantic than the actual series.
5. Full Moon wo Sagashite is a music anime so inevitably the music has to be good. I loved all of Changin' My Life's songs for this anime and Myco truly made "Mitsuki" shine. My favorite songs, if I had to pick one, would be first ending "Myself" (though my ultimate favorite would be Route L version of "Eternal Snow," which I wish was longer and recorded with better acoustics.) Nonetheless, I pick for best ending "New Future" because I just love how they use the song in the last episode and it ties the whole anime together-- it really brought tears to my eyes. And I loved how Tanemura Arina tied in the "New Future" lyrics in volume 7 of the manga. Anyhow, love them all.
6. Naruto's 1st ending theme Wind by Akeboshi. I know it's a cliched choice, yet is there any other subsequent ending theme that fits "Naruto" so well? I personally find this one of the most beautiful and poignant anime ending themes ever, the way it starts out with the flute, the vocals kick in, even the wispy animation. This was my first introduction to Akeboshi, and I fell in love with his music and lyrics. They are simple yet so poignant, and Japanese mixed in with a Celtic flair was very refreshing from the typical pop scene. I really like "Yellow Moon" as well which has been on my playlist quite frequently. Someday, I will catch up with Naruto Shippuden.
7. Wolf's Rain - "Gravity" by Maaya Sakamoto. You can't go wrong with Maaya meets Yoko Kanno, and this song, with complete English lyrics is a hauntingly memorable ending. I haven't watched the anime yet, and the ending sequence animation is boring, but I love the ending. I first heard just a short clip of the song at the end of an anime and then set out on a quest to find the song--I didn't even realize it was a Japanese anime song let alone Maaya.
8. Beck Mongolian Chop Squad Ending 2: Sowelu - "Moon on the Water." Good songs bring you back to the moment you hear them. The first time I heard the acapella duet between "Koyuki" and "Maho," it was 5 am sophomore year of college on the day we had to sign up for courses online for the spring semester at 8 am sharp (yes, it was a battle of speed), and I had not yet decided my classes. I was procrastinating and began watching Beck, and I still remember the shiver I felt down my spine when I heard the guitar strumming in and the clarity of Sowelu's voice (of course, I didn't know she was the singing voice of Maho then.)
9. Inuyasha - Do As Infinity - "Fukai Mori." DAI was one of my earliest J-pop hooks, and this probably is my favorite DAI song. Inuyasha, like many Shounen Jump anime, has great songs. Ending 4 Boa's "Every Heart" is also a favorite.
10. Nodame Cantabile's 1st ending "Konna Chikan de..." Yes, this song does it too--I love it when the beginning notes kick in at the end of the episode--this song gives me a warm, fuzzy feeling, and the lyrics are so cute too. (Makes you nostalgic hearing Tomokazu Seki aka Kinomoto Touya as Chiaki-senpai. Their personalities are actually surprisingly similar, down to the violin-playing. Lol.
Other notable anime ending themes.
Mahoujin Guru Guru - "Wind Climbing" I first heart the ending done in Korean, and the song is strangely memorable though anime itself is cute and silly. It still retains much popularity in Japan as well, it seems, according to polls.
Bleach ending 3 - Youhna - "Houki Boushi" The singer is actually Korean, and though I was introduced to her because of Bleach, I enjoy her Korean songs as well--she is talented and a breath of fresh air in the K-pop scene. I especially love this ending because the animation changed each episode to match a division. How awesome is that? Bleach, like FMA, boasts an awesome repertoire of theme songs, (unlike Naruto which is a hit or miss for me.)
Macross Frontier Ending 1 - May'n - "Diamond Crevasse." Since Macross is mecha music anime meets Yoko Kanno, of course it should have a spot on the list. I loved many songs on the soundtrack; I personally prefer Megumi's voice to May'n's voice, and my favorite song is "Ao no Ether." But Diamond Crevasse, I believe, is THE song of Macross. I love all subsequent versions of it.
Nana Ending 1 - Olivia's aka Reira's "A Little Pain." I think it's the best song of the bunch in another music-centric anime.
K-on Ending 1 - "Don't Say Lazy," which I don't think needs anymore pimping than the hype it has already gotten.
Slam Dunk Ending 2 Wands - "Sekai ga Owaru Made Wa"
Saint Tail Ending 1 - "Junshin "
Rurouni Kenshin Ending 3 - T.M. Revolution - "Heart of Sword."
Lastly, the Fancy Lala Ending Theme. The plotline is the typical young girl transformed into older popstar story. There was nothing outstanding about this anime (which was supposedly overshadowed by the reigning shoujo anime of the time, Card Captor Sakura). It is a typical coming of age story, but the last episode which segued into the ending theme really made this anime linger longer than just another typical magical shoujo anime. I actually prefer the Korean dub of the song, which is rare for me.
Favorite opening themes I think would be easier to do because openings have bigger animation budgets usually and need to capture the audience and are better publicized/ easier for me to recall. I feel like anime OPs should draw you in, and I do value good opening theme animation sequences. But with ending themes, I like songs that gives you a lingering sense after the episode has ended (hence oftentimes the more ballady ending themes in contrast with upbeat openings). With my favorite songs, I think there is a pattern of a. music animes, b. shounen anime c. anime I watched as a child d. anything involving Yoko Kanno or Maaya Sakamoto or both. You will see this pattern manifested more in the next list I make. ^_^