Most retro crap on the Internet is garbage: It's like, here's a T shirt with some character from Mr. Belvedere on it that you don't even remember LOL!
Retro for the sake of retro is lame. If you're gonna talk retro, bring something new into the mix …which is why Super Mario Crossover is so sweet.
The idea is simple: Play the original Super Mario Bros. with a selection of other NES classic characters. There's Samus from Metroid, Link, Mario himself, Mega Man, Simon from Castlevania, and the dude from Contra who's name no one knows or cares about.
What makes it interesting is that each character retains their signature moves from their own games. For some characters it's a bitch: Like Samus is too tall to squat down and shoot at Goombas. I've gained a lot of respect for all the hard work Mario and Luigi have done over the years.
It might not be the most fun you've ever had, but it is interesting, and will remind you why Link is such a pussy. Give the game a try here before any of the multiple copyright holders who's rights are being infringed upon file a complaint.