Skipped over Great Battle II and III because they looked pretty lousy for beatemups, ended up at IV which was a decent platformer, if a little overlong. The easiest comparison would probably be Mega Man X, with somewhat similar aesthetics (especially one level with a striking resemblance to Storm Eagle's) and mechanics. You have to switch between all the player characters a good amount for certain situations, making each one at least decently useful. Except, tragically, Kamen Rider. Justice for Kamen Rider.

There are also these arduous one-on-one mech battles at certain points in the game not unlike the ones in Rocket Knight Adventures, featuring a totally different set of rules from the rest of the game. Quite clunky, quite frustrating, easily the worst aspect here, but I didn't think it was necessarily bad enough to deduct points.