Hulk vs. Grimlock
Hulk: Hah! Tall changing machine man thinks he can scare Hulk. Hulk strongest there is - Hulk smash you!
Grimlock: Bah! Puny green human is full of empty threats. Grimlock will teach you who is strongest! Prepare for my bite!
Grimlock uses both T-Rex and Robot modes during clash. And...?
well, optimus prime is aparantly in the class 100 strength level, so i wouldnt put grimlock much lower. id say hes more durable than the hulk, but wouldnt heal after taking damage. hes suposedly fairly intellegent, despite his primitive vocabulary. plus he has a big firepower advantage in robot mode.
i can see him using it for ranged attacks but nothing more as its more vunerable that his t rex form. in fact, even being thrown around by devastator i cant remember him ever taking any real damage, even in the movie when he took a massive kick while falling from the sky he was up and ready to take on the sweeps when they came back. so he might have needed some minor repairs, or have been either knocked too far away to return to fight devastator, or could have recovered on his own shortly after.
so while the hulk is seeminly the favourite i wouldnt count out grimlock. i think it would be around 50/50. grimlock has better firepower and is supposedly a reasonable tactition.
If I were Grimlock, I'd fight in Robot mode for more manuerability. Hulk leaps at Grimlock, hw can swat him away with his energy sword, then blast him with his rifle where he falls. A determined Hulk could do some damage to Grimlock's legs or an arm, but if Grim keeps his big size advantage working, it looks good for him.
Quick look at my Transformers Universe claims Optimus Prime can lift 4000,000 pounds ( or 2,000 tons) but that looks like a mistake in printing; it would make him way stronger than giants like Superion and Predaking. More likely 400,000 ( 200 tons), and Grimlock is arguably second only to Op.