I never played the original Pokemon (1st Gen), instead started playing Silver/Gold (2nd Gen) after influenced by the cartoon, but end up skipping the next generation (3rd Gen) after my interest faded.
It was not until DS era that I start picking up Pokemon again (4th and 5th Gen).
The game I was playing 'all day and night' on my GBA is Fire Emblem. I literally thought that was the best game ever created for GBA, and possibly the best SRPG, ever.
I would go so far to say I brought my current 3DS for Fire Emblem Awakening too. Moreso than the recently announced Pokemon game for 3DS.