"Welcome to Die!" (or, X-Men: The Arcade Game)

No contest, this was my favorite arcade game as a kid (with Teenage Mutant Ninja Turtles and the Simpsons coming in at 2nd and 3rd, respectively).

Gameplay was fun and fast-paced; graphics were sharp and vibrant; all the bosses at the end of each level were cool; and best of all, you could play with all six X-Men (Nightcrawler, Wolverine, Colossus, Storm, Cyclops, and Dazzler) at the same time. It was the best when you could get everything organized and strategic, making sure everyone was on the same page and understands the plan of attack. This usually meant one half of the team would fight off the Sentinels coming from the right side of the screen with the other half taking care of the left side's Sentinels, which ultimately resulted in everyone covering everyone else's back. And then by the end of the level, everyone could use their mutant power (which we all wisely saved) to gang up on the Blob or the Juggernaut or Mystique or whoever the boss was.

This is obviously something that could only happen in my wildest and zaniest of dreams, but it'd be amazing to actually own one of these and have it in my house and be able to play it anytime I want.