Still hard, and I know that there's a lot of good anime I haven't seen, but some good ones... hmm...
-Serial Experiments Lain - awesome and unique cyberpunk-style anime
-Haibane Renmei - just as good as Lain, if completely different... (fantasy-ish, but different...) great show.
-Escaflowne - pretty good.
-Princess Mononoke - Ghibli/Miyazaki at their best...
I don't know... lists are hard (to keep the number of titles mentioned down) Love Hina is pretty good... Excel Saga is awesome... (I thought Magical Shopping Arcade Abenobashi (Abenobashi Mahou Shoutengai) was good, until I saw Excel Saga...
I liked Full Metal Panic... (Fumoffu is cool too, but I haven't seen it all, and I LIKED the drama parts too, which Fumoffu does away with...) oh, and I need to mention To Heart and Kanon. Liked both of those a lot (Kanon for being interesting within its field, and To Heart for ... completely calm and slow paced I guess? It worked...).
There is lots of good anime out there... for longer serieses, InuYasha and Ruroni Kenshin are both pretty good... Ranma too I guess, though the complete lack of character development gets old after a while (absolutely none through the entire series for any character!).
There's 10. Well 11, but close enough.
Others that I could mention, but probably not as good as the above...
Tenchi... just saw the OVAs, those were good. Cliched, but good.
I also have to mention Vampire Princess Miyu (both the OVA and TV series). Good series, I like it... sad and depressing and full of people dying tragic young deaths (or other forms of ... permanant mental disruption...), but good.
I've had Miyu wallpaper on my computer for quite a while now... (following ones from Starcraft, Kanon, Haibane Renmei, Lain (this one with blue and grey and a field of ominous power lines... you'd understand if you've seen the series...), etc...)
Oh, and Yu-Gi-Oh isn't that bad, even if it is seriously cliched and lame a lot of the time...
(though the original cast is better than the new GX one...)
One Piece and Naruto seem decent, until you realize how they make the shows long by just having everything ... take ... several ... dozen ... episodes ... to ... happen ... when ... it ... could ... be ... done ... in ... one ... they are still somewhat addictive, but tedious after a while for sure. Not on a 'best of' list. Sure, InuYasha arcs last a while, and Kenshin fights might go on for a few episodes, but those shows aren't nearly as bad as these ones...
But there's lots of decent-to-good anime out there. From other American TV stuff, Gad Guard and Gatekeepers 2021 on TechTV/G4TechTV were good, from their lineup... not 'top 10' material though for sure. They showed some other good stuff, but I can't remember it, as I didn't have access to the channel very often...
On that level I could also mention Angelic Layer, from club. A solid good anime that was well worth watching.
Oh, as for the original question, 'which one is your favorite', I'd probably choose from one of the two on the top of the list, Haibane Renmei or Lain...