I LOVED Stadium 2 when it came out. Stadium 1 was great, but Stadium 2 was better in almost all areas, plus it supported Gold/Silver/Crystal which made it even better in my eyes. The Johto Gym Leader Castle was epic too, much more so IMO than Stadium 1's was. The design of the castle menu made it feel like you were traversing a board game :)
I'm also really enjoying Pokemon Rumble atm, it's a fun quirky little game, good for when you want to play something but don't necessarily want to sit down for three hours to accomplish anything. Pokemon TCG for Game Boy is another great one for me, too. It's the main reason I kept my GBA SP, so I can play it on the go every once in a while. (Game Boy Player for GC is great too, but it seems to like erasing my games when I'm done using it. *shrugs*)