Backwards compatibility has always been a mainstay for Nintendo's portable systems, with every single new iteration reaching back toward the past to play legacy content. Even the Nintendo DS, third cousin twice-removed of the original Game Boy line, has a convenient second slot to play GBA titles, but it's not perfect. The slot is unable to play original Game Boy or Game Boy Color games, and for us old-schoolers, that's a bit of a buzzkill.
Does this even matter to you? Remember, the original Pokemon Red/Blue titles were original GB titles, as were classics such as Metroid II, Super Mario Land, and even the very first Tetris. We also miss out on the brilliant duo of Zelda: Oracle of Ages and Zelda: Oracle of Seasons for the Game Boy Color, that system's final swan song. Do you still keep around a GBA (or older) system for playing these titles, or did you trade it in for store credit for your shiny new DS? Which game from the GB/GBC era was your favorite? And remember, if you answer ... we know you're old.