Actually, IMO, battlefield2142 had the best 'feel' of a giant, lumbering mech. The mechwarrior series is too... smooth. Your guns dont jostle around w/ every step you take, you view out of the cockpit doesnt bounce hardly at all, etc.
I BF2142, the walkers felt much more stompy to me. You even had to learn to compensate for your side to side lumbering mech when you fired your guns. It was quite nice.