I totally agree with Chad about making the heros superhuman. I've often said that is exactly the difference that makes Indiana Jones movies good and Tomb Raider movies bad -- Indy's vulnerability. It's the same reason that a videogame quickly becomes boring after you turn on cheats like god mode. Winning is no fun if there is no risk of losing. It's also why I find Superman to be such a crappy Superhero. He's basically Jesus + invulnerability + almost all the superpowers. He doesn't risk anything by going up against the bad guys. But I digress . . .
I disagree about what makes an actor. Acting, even acting like yourself is difficult. It's obviously easy to be yourself in real life. Delivering memorized lines, however, so they sound spontaneous and authentic, even with your own personality, is difficult, and few people can do it convincingly. If that's the only personality he can do, then he's a character actor. He lacks versatility. Nevertheless, I've always thought he's done a really good job and been entertained by him in movies. I've only seen him in Holes, Constantine, Transformers and Surf's Up. I've seen iRobot, but I can't for the life of me remember him being in it. The movie wasn't very good, though. I hated Transformers, but I didn't have a problem with him. I thought he was great in Constantine and, contrary to Chad's assertion, he's totally different in Surf's Up. Maybe that's different, though, since he's only providing a voice, and not the whole nine yards. Nevertheless, he was very convincing as a teenage surfer.