I've been playing a lot of original GameBoy games lately. Pound for pound, I think it has one of the best libraries of any 8 or 16 bit console. I've been playing Donkey Kong, Final Fantasy Legend, Operation C, Fortified Zone, Double Dragon 1 & 2, and Cat Trap among others. There are just tons of cool pick up and play games for it. I sometimes wonder if devs just had more creative freedom because it was treated like a more limited NES. Also, I think the fact that it's a handheld forced them to keep things more succinct. The result was tons of fast action and addictive games that never seemed to ask for too much.
I would urge anyone to at least emulate the system and play around with it's library for a bit. You won't be disappointed. I say all this about the GB, and I'm not even a fan of handhelds.