First: (No) Anime over 26 episodes will be good. They are for promoting crap to children. There are a few execeptions (Full Metal Alchimist, maybe Rurouni Kenshin)
Every few years a REALLY good Anime will be produced. It is very hard to find them, you have to watch a lot of crap to get them *g*.
My list (yeah i repeat much of the shows already mentioned)
Must see:
Cowboy Bebop, Gungrave (yeah first episode is crap but then it is a work of art), Berserk (if you are a MAN *g*). Maybe Avatar (Yes i know it is American... but who cares?) Maybe Death Note
Can be cool:
Hellsing, Trigun, Code Geass, Rurouni Kenshin (OVA is very good), Ghost in the Shell: Stand alone Complex, Full metal Panic: Fumoffu... And many, MANY more
what i love about anime is, that it can be really weird, or be really... normal and still be made. Hollywood wouldn't think about producing something which would be so "risky".
I once saw a series about a bartender, who always knew what kind of drink a person would need. Really... it just showed normal people with a problem. They entered the bar, got their drink and then they would remember something, or relax and so defeat their inner demons, or think their life over. And that's it. Think such a show could be made somehow else than in an Anime?
and to be a bit more helpful:
http://www.animenfo.com/statistic/top.php?type=anime
very good site