I'll second TMNT: Turtles in Time. The train and hoverboard levels kicked an unreasonable amount of ass.
The game that owned all my time though? God-fucking-zilla. How it played was like this: First, an you would be given an overhead veiw of a map, you at one end, the monster you need to kill at the other. You were a blue dot. A. Blue. Friggen. Dot. You would move square by square, avoiding mines, tanks, and rocket launchers (or step on them by moving your dot over them), untill you met your enemy.
You were timed. The reason? Humans were controling Godzilla and the transponder would run out of power. After you met your enemy, the game would switch to a Street-Fighter side veiw, and the battle would be on! To attack, you would punch your enemy, and then back up. As you backed up, a tiny box at the top of the screen would show pictures of attacks. These pictures were random. To use the attack, you would stop moving (you may have had to press a button also, can't remember). Then, an animation would appear showing Godzilla doing the move.
It was single player, and you could only play as the big G himself. Also, one of the bosses (Mothra), made it so you could only kill him/her/it by using the rarest of your attacks (Hyper beam). The reason? Mothra could fly, and all your other attacks would miss. Even your normal energy beam attack could not gain the hight and speed needed to hit.
Looking back, it was the worst game I have ever played, and the creator has earned a seat in hell in between Uwe Boll and whoever made Superman 64. But I'll say this much, if ever I have the chance, I will play it again until my hands bleed if only to remember how awesome and big it made me feel.