Sonic the Hedgehog 2 is easy. I don't mean to say that it's too easy, because it's a very fun game (and the high point of the franchise in my opinion), I mean to say that the first time I sat down to play it at age 11, I got to the final level. It's beautiful, it's memorable, it's got a absolutely golden soundtrack... it just doesn't have a lot in terms of challenge. Even the vaunted Metropolis zone isn't hard, it's mostly just a little annoying, and even then, it's not hard to simply breeze through it to get to the beautiful Sky Chase and Wing Fortress Zones.
Then you reach the Death Egg Zone.
It's not really a 'zone' per se, it's more of a boss rush - with two fairly difficult bosses. Since there are no rings to be found, any hit during the rush will kill you and send you to the beginning of the stage. First, you play against a taller, metal version of yourself. With a little persistance, it's not hard to figure out his pattern, but it takes a bit of doing. Victory assured, you run towards the evil Dr. Robotnik. Every gimmicky rattletrap 'boss' he's taken up shelter in throughout the first two games (even the final boss of the first game) has been pathetically easy. Robotnik runs away (somehow outrunning the self-proclaimed "fastest thing alive" in the process)...
...and jumps into a massive armed robot. The fight is ridiculous, the pattern is difficult to remember, the hit box on the robot itself is often hard to hit. And instead of the usual '3 hit and quit' that every one of his other iterations have been to this point, this one takes twelve.
It took me hundreds of lives over the course of dozens of tries at it before I finally took it down. Needless to say. Defeating it was cause for absolute, fist-pumping celebration.