I love anime theme songs! They're usually pretty good for putting you in the correct mood for the anime. And of course, liking the song will usually increase your enjoyment of the anime. Luckily, if you don't like the theme song, it doesn't damper how much you like the anime... you just skip the song. Once in a great while.. you might find an anime intro (or ending) that you really like, but don't care for the anime.

Example:

Anime - Ceres, Intro - Scarlet
I love the opening song... (to no end), and I love the anime.
Love all around! ^_^

Anime - Ouran High School Host Club, Intro - Kiss, Kiss, fall in love
The opening is too peppy for me I think, but I LOVE the anime!
Skip the intro, and go directly to my love!

Anime - El Hazard, Intro - Illusion
I like the intro very much. I like the sound of it... Absolutely detest the anime.
Downloaded the intro song so I could enjoy the love.

Yeah, I know exactly how ya feel. Alot of songs in my mp3 folder are comprised of anime theme songs, and ending songs. I got....tons of these songs, now that I think about it. Personal favorites are the Neon Genesis Evangelion theme song, "Cruel Angel's Thesis", and the two songs they used for the Ghost In The Shell: Stand Alone Complex series. The art of anime openings was something that I thought to be very, very interesting, and I'd like to see more shows on television have special openings like that. The only American TV show that I can think that has a musical-based opening (bear in mind, I don't watch TV that much) would be the Showtime show Weeds.

I also know a few Adult Swim cartoons have their own lil openings....

I love the songs Melissa, by Porno Graffitti. and that other song by Nana Kitade.. I can't remember the name of the song but it is really good. They were both songs for Full Metal Alchemist.

I also liked this song called Myself which was in the anime, Full Moon Wo Sagashite. That song was performed by Changin' My Life.

I really like the Hey Jimmy song from PeaceMakerKurogane (ending theme). Just something about it and the bounciness made it rule.

I'm sure there are more that I liked, but I can't recall any past the one.

Man there are a ton of anime theme songs that I like. Some I have seen the shows such as Rinbu Revolution from Utena, Cruel Angel's Thesis from Eva. Some on the other hand I haven't seen one episode but I'm in love with the song such as Taiyou no Hana from Cyberteam in Akihabara or Over The Sky from Last Exhile. The style of the theme songs I like vary too. I like stuff ranging from Ready Steady Go, to Let Me Be With You to Theme of Gemini to Tank!. It all varies and it's all good!

Ya know, now that I think about it, I agree with PHD that the opening theme to ElHazard Really does kick major ass.

I liked the one theme to Noir... Til I watched Noir and it was played repeatedly Over and Over again.. Now I'm sorta eh with it.

All of the music from the FF AdventChildren movie ruled =D

There's a theme from CardCaptors that I also really like, but I forgot which one.

Last but not least for this post, the theme from SpiritedAway when San is on the train. It makes me want to cry. It rules So much.