I'm going to give you a bunch of dubs, because I've watched them in dub & they were pretty golden. Most of these are popular enough where they have the classic cast of voice actors (that are good).

I gave you up to G, since I have a bunch, but start here :) My fave's are Cowboy Bebop & Death Note (these are great)

.hack
	//sign (start with //sign, but all the .hack's are cool):
		http://www.watchcartoononline.com/anime/hacksign

Accel World (speed up your world, kewl program that's shared between young kids, when you lose, it's erased from your memories; this is the follow up to SAO (sword art online)):
	http://www.watchcartoononline.com/anime/accel-world

Angel Beats (ah, such a goodie, afterlife, comedy, pretty ladies, great music):
	http://www.watchcartoononline.com/anime/angel-beats

Animatrix (if you haven't seen this, then you really need to; it's a fun backstory to a bunch of the matrix):
	http://www.watchcartoononline.com/anime/animatrix

Arimitage III (haven't watched this in a while, but it's a mind bender, kinda like ghost in the shell, humanoid robots, really neato):
	http://www.watchcartoononline.com/anime/armitage-iii

Cowboy Bebop (This is required++, it's a classic, perfect dubs, amazing story, omg!):
	http://www.watchcartoononline.com/anime/cowboy-bebop

D.Gray-Man (kinda like pokemon in humor, but with a really neat interpretation on ghosts, bringing people back to life, torment of souls):
	http://www.watchcartoononline.com/anime/d-gray-man-english-dubbed-guide

Deadman Wonderland (people on death row, neat hidden stuff in the prison with superpowered freaks, very fun to watch):
	http://www.watchcartoononline.com/anime/deadman-wonderland

Deathnote (one of my all time favorites, total mind fuck, characters do a lot of trying to think like the other's and vocalizing it via monologue, great!):
	http://www.watchcartoononline.com/anime/death-note

Guilty Crown (crazy awesome, this kid pulls out weapons from his peers, sexy main protagonist, amazing music):
	http://www.watchcartoononline.com/anime/guilty-crown