The Glee starlet isn't a singer. We know this. She was brought into Glee to give it some acting chops. Even her character has decided to chase an acting as a career instead of singing. She had a small bit appearance in Burlesque and was the love interest in the ho-hum average sci-fi romp I Am Number Four. She would be a good choice to play such a strong and prominent comic book heroine simply because she straddles the line of bitch and confidence well enough that she is a true enigma.
Enver Gjokaj as Mr. Fantastic (Reed Richards)
The man stole every scene he was in in Dollhouse, even playing the brain-swapped gender bend of a sexy college girl trying to sleep her way to the top. His craft was illustrated in Dollhouse well, but this would be his chance to shine that he can play with the big boys. If you don't believe me simply watch the second season of Dollhouse to see the amount of fluidity and depth the man has. He could pull of the traditional "I am way above average looks but don't know it" nerd that is Reed Richards with little effort and it would still be a joy to watch on screen.
Kevin James as The Thing (Ben Grimm)
To me the character of The Thing has always been epitomized as a giant brute who can deliver one hell of a punch but has a heart of gold. And that description fits Kevin James to the t. While he typically sticks to comedy rolls, The Thing and The Human Torch have always had a brotherly like banter going on, even in the most heated moments of battle. The action and clever world play would allow us to see what the man can do in different situations and given his track record I would love to see him yell "It's clobbering time!" while punching some baddies in the face.
Zachary Levi as The Human Torch (Johnny Storm)
Any fan of Chuck will tell you that this guy can deliver on the action. Anyone following him on twitter knows he is a huge nerd. He is also sassy enough that the banter from Ben Grimm and him would be legendary. He also has this hero like swagger that exudes confidence without showing arrogance. A perfect choice for the Human Torch.