I've played AD&D v2 and v3, Gurps, D20, Palladium, Cyberpunk, & Warhammer. Of those, I prefer AD&D v3 and D20. The biggest weakness of AD&D v3 IMO is the poor quality of the monsters in the Monster Manual. I spend a lot of time for my games converting AD&D v2 monsters to AD&D v3 format. Why they left out things like the Cave Fisher baffles me.Palladium is good at lower levels, but the characters become over-powerful at high levels and it gets a bit silly. The only one that I couldn't stand was Warhammer - I was bored to tears in a very short time.
I've never played Call of Cthulhu, or AD&D4. I had a good look at AD&D v4, but came to the conclusion that this was an example of change for change's sake (or, more likely, to get people to buy new books) and that the V4 game was not as good as the V3 game.