I remember liking the first Ace Ventura but hating the second. I was in junior high or high school when I saw the first, though, so I'm not really sure whether it was actually good. But he has unquestionably been in far better movies. Truman Show is amazing. Eternal Sunshine of the Spotless Mind is a ---smurfing--- masterpiece. Man on the Moon was pretty good too.
Edit: Except the scene where he's conducting surveillance from a fake rhino and the fan breaks and he can't get out and then the rhino gives birth to him. If that was in the 2nd movie, it at least had one good scene.
That scene is the second one, and I agree with you, the first was much better, but the second has its moments
Truman show: didnt like or hate it
The Majestic: terrible
The Mask: very meh
Dumb and Dumber: I liked,but not because of him
Batman Forever was just terrible (not his fault)
Me Myself and Irene: was great but not one of my all time fave comedies but its close, add this to the list of JC movies I can watch
Bruce almighty was just plain bad
Man on the Moon: best movie he ever did and I love, not on the list cause not a comedy (more like a biography)
Yes Man: I didn't like it, but I don't have kids to watch it with and I'm sure that's why
The Number 23: Lame
Fun with Dick and Jane: mediocre but again it was the script or lack there of.
Back to Ace Ventura, the whole movie is pretty funny from beginning to end. The open HDS package scene is hilarious, and even some of the more zany parts like the shark tank and lookin at all the dolphin player's rings keep you entertained. Cannibal Corpse cameo? hello?! yes please!

The ONLY scene in "Cable Guy" that made me laugh is the scene when he visits matthew broderick in jail and thats only because I saw midnight express (on VHS!)