Okay...
Gorillaz (not The Gorillaz ;)) is made up of a few guys portrayed by cartoons--1) This is of course not their first album. In fact it's their (I think) third. 2) They're an excellent grouping of semi-electronica, semi-rap concoctions, more rap on their first two CDs, more electronica-type beats in this one. 3) If you liked Feel Good Inc., you are not anywhere near guaranteed to like any other songs by them. It's not the same as a lot of their other stuff
The main thing I've noticed is the parity of them and Deltron 3030 and Del the Funkee Homosapien. The styles are VERY similar, so if you end up liking Gorillaz, then you'll end up liking the others probably.
I suggest picking up their album Demon Dayz, what Feel Good Inc. is off of, and listening through it. Chances are you'll really like it, though I can't guarantee anything. From there, check out their self-titled album and see how you like it. I'd also suggest testing the waters out on Deltron 3030 with their album Virus.
Yeah, that about covers it.