I'm looking forward to seeing Colossus in X3, although I agree that if he isn't colossal, it'll be a real shame. I hated the CGI Hulk, but at least he was massive. That was one of my main complaints about the Thing in the FF movie. I didn't mind the rubber suit (it gave the actor the chance to actually act). I just didn't like that wasn't big and bulky.
I know that the Thing in the beginning of the comics was smaller and more lumpy, so we can hope that if they make another movie, they will incorporate a story line that has him evolving towards his larger, more rocky/angular look.
And, as for making characters such as Colossus, Thing, and Juggernaut look larger than other characters, they don't need any fancy-schmancy effects. Remember how they did the hobbits and dwarves in LOTR. They just used some old-fashioned movie magic like split-screens and stand-ins.
Thayne, if you haven't seen Rocketeer, I highly recommend renting and watching it, preferably on a big screen. It's alot of fun, especially if you know the comic book and are a fan. The sets and flying scenes alone are worth the price of the rental. And the rocket kicks a$$! And, if you don't like it, I'll personally refund you the cost of the rental!