If I had to pick the funniest CGI film of all time, it would be Cloudy with a Chance of Meatballs which wasn't made by Pixar or Dreamworks, and it was still visually impressive considering it was one of (or the? not sure if you wanna count Horton Hears a Who!) the first CGI films to use overly cartoony animation that you still can't really find in any other CGI film.
I mean sure, Pixar and Dreamworks and scuh will use stretch and squash, but the way the Cloudy characters moved, the expressions they made, you don't see stuff like that very often in CGI works.
I will agree SOMEWHAT on the Looney Tunes vs. Disney debate, but more on a level of what I'm feeling. I might change Looney Tunes to MGM Tex Avery however.
If I want to watch a cartoon with technical impressiveness with a building story and characters that you grow to like and care for their problems, I'll probably go with Disney. If I want to watch wackiness and silly humor but still based around characters that I will also enjoy seeing on screen, I'll go watch Tex Avery.
I also don't know why people keep pulling out old films as slander against Dreamworks, like Shark Tale. That was so long ago and based on what Dreamworks has done now, I say they have come a long way from Shark Tale.
I would say really the only truly hit and miss thing Dreamworks has had lately would be Shrek 4, but by then, critical audiences were sick of Shrek so we all know this was mainly a ploy for money. Monsters vs. Aliens was decent enough to good by some eyes, Kung Fu Panda and How to Train your Dragon are well loved, and now we have Megamind which is supposedly hilarious according to some people here.
Pixar, I think, has gotten more humor gentle and story-based as time went by. Toy Story, Monsters Inc., A Bugs Life had a bit more zip to them. The Incredibles was pretty dark and only had a few laugh-out-loud moments, then there's things like WALL-E, Up! and even Toy Story 3 which have more serious, "i'm capturing your attention for the story" moments than laughter.
Not to say that Pixar's movies are boring, it's all so opinion based it's weird. By myself, I don't laugh very often at Pixar, but my attention is grabbed instantly by it. But when I watch it with a friend, who has a way of making things funny no matter what, he ends up opening up how funny everything is in Pixar, such as the loud sound that Kevin makes in Up! which he found was hilarious and started imitating it, which made me start laughing.
So yeah, I would agree with the OP on some level. I feel more like Dreamworks = casual while Pixar = serious.
And with Megamind out, which I cannot wait to see since I LOVED the trailers, it'll probably only boost my opinon on it more.
And just remember, Pixar has a ton of sequels coming out too, one of them is based on Cars which last time I checked, wasn't their most popular film. And it has a generic plot that ever big race story has. Pixar will probably have their fair share of crapper sequels like Dreamworks.