I'm about four months behind the gaming blogs on this, but you need to go play VVVVVV right the hell now. You can try a two-level demo over at Kongregate and once you become thoroughly addicted, you can purchase the full version (fifteen bucks) on the official site.
I've never had much of a yen to play old-school style games since I started using a computer that could execute something outside of DOS games and an NES emulator. I'll come right out and say it: older games are way, way too hard for me. I get frustrated very easily. Until I received a Game Genie, I don't think I saw an ending to a single one of my Nintendo games, even with it I didn't finish many of my games. This led to the fact that as I got more powerful computers, I would play fighting games almost exclusively. They were fast, not terribly complex if you didn't want them to be and full of instant gratification. Turns out this is exactly why I love VVVVVV.
All you get is handful of colors and a player sprite with two, coun't em, two facial expressions. Your little guy ventures from room to room, scrolling between them Metroid-style. Each room presents a challenge for the only technique your little guy has: flipping gravity. Hit the Action Button and he flips onto the ceiling. Hit it again and he drops. It only works when he's standing on a surface, so you can't flip in the air. That's it. The rooms, in turn, becomes individual puzzles varying from laughably easy to come on comeoncomeon AGH! DAMMIT!. There's usually one exact way through and it's up to you to divine it. Oh. And there are spikes, odd sprites and various other dangers all floating about. When you die, you respawn at the last waystation you hit, which, depending on the difficulty of the puzzle, may be in the same room or five spike-filled and twitch reflex-demanding rooms away. There are no lives, no continues. You die, you respawn, you try again, you die, you respawn and eventually you figure it out. Well, usually, at least – I've had to find the solution to at least one room online. The odd thing is that watching the game is more frustrating than actually playing it. Each room, each puzzle is so minimalist that you know you can do it, god dammit, and you keep trying. While punishing (oh is it ever punishing) the game never throws something at you that you can't do. It's all about nerves and reflexes.
After you check it out, take a look at developer Terry Cavanaugh's site, where he keeps links to a number of his other games. Don't Look back is another gem, although more of a conventional platformer. Oh, and here is where you can get Souleye's PPPPPP, the soundtrack. I'm usually very way about listening to chiptune for too long, but the quality combined with the style of the game makes it eminently listenable. Here's my favorite track, “Potential For Anything”: