I think it will be pretty hard to boil it down as there are different genres. So I add a few who stand out in their respective genres which everyone should give a go.
Shonen
1) Dragonball/Z
2) One piece
3) Yu Yu Hakusho
4) Full Metal Alchemist
5) Death Note
6) Detective Conan
Seinen
1) Cowboy Bebop
2) Outlaw Stars
3) Berserk
4) Monster
5) Trigun
6) Claymore
Mech
1) Gundam (Wing, G, 00, Z)
2) Gurren Lagann
3) Code Geass
4) Neon Evanglion Genesis
Sport
1) Slam Dunk
2) Hajime No Ippo
3) Eyeshield 21
Haven't really delved into other genres such as slice of life etc.... Here's a breakdown in great animes in their categories. Alot more I could think off to warrent a list but can't be asked as it could take a while.
"Life is but a gentle death. Fate is but a sickness that results in extinction and in the midst of all the uncertainty, lies resolve."
