Saints Row 2 is the best worst GTA-like. The best, because, well, it is the silliest and funniest one since GTA2. It is an absolute blast to play.
Worst because the port to PC was absolutely crap. It CAN be fixed with two mods, but it is still far from ideal.
The two mods are these: http://saintsrowpowertools.com
It fixes (some) performance issues and makes it work. Yeah. Don't play without it.
Hell, you basically CAN'T play without it. http://idolninja.com/sr2.php
Gentlemen of the Row. Great mod. Adds a shitload of silly stuff, tries to restore content, and last time I checked, was even porting the SR2 DLC that never got released on PC. Besides, flamingo nukes.
Making the best GTA-like even better. I don't think it has things as silly as SR3's dildo weapons, but it is close. Have not played SR3, but Gentlemen of the Row is wonderful and great. Unlocks animations and voices and A LOT OF STUFF ot be used.
Also, once that is done and configured, you can do AWESOME coop multiplayer. It is a blast. At less than five bucks, SR2 is a TOTAL STEAL. Hell, I don't really like GTA, but SR2 is amazing.
So I tried the 'vanilla' SR2 and it basically made me despise the series. Will the mods really fix what was a very, very, very, very rough gem?