The only games I've played on Gameboy was pokemon games. So I would have to say Leaf Green.
I feel really old lol. Seeing that so few people on this thread have actually played original Game Boy games.......
Some of my favorites on the original Game Boy are Pokemon R/B/Y, Tetris, Navy SEALS, and Pokemon Silver (it played on the original Game Boy as well). Other ones that I've played include Star Wars (ported to the Game Boy from the NES version) and Star Wars Yoda Stories.
Actually thinking about getting the original "brick" Game Boy from Ebay just for fun, the battery life is insanely good, better than any handheld in history (up to 40 hours, the 3DS has nothing on that lol). Only problem is that pea-soup colored green screen, saw it first hand on my best friend's Game Boy when I was a kid. Then again, I might just get a GBA for my old games, since I just sold my Game Boy Pocket.
Makes me feel old too lol
I actually still have my brick Game Boy stored away, and I will not, under any circumstances, get rid of it. Actually, I only put it away a few years ago when I got my Pokemon LeafGreen version, and started playing D/P/P.
The colors are a bit off, but when you've played the thing for years, they kind of look normal
Yep, it was so classic. The only doubt I have about buying one is the screen quality. From what I remember back when I was a kid years back, the screen was legible, and it wasn't all that bad (my friend was always playing Ducktales on it). But all the reviews that I've read now say that it's blurry, with hard-to-see faint graphics. Is the screen really all that bad?
The battery life was really epic, though. 40 hours on 4 AA's.
Probably Link's Awakening.