...pretty much all of these. I don't think I ever actually finished the "main" part of either Pokemon Stadium 1 or 2 because of all the awesome minigames. In 2, you could even transfer your winnings over to Gold/Silver/Crystal in the form of extra casino tokens, which made it pretty damn lucrative.
Seriously, 95%+ of my time in both Stadium games were either playing minigames or at the GBC tower, where you could play your games in color, Super Game Boy style, on the TV through the Transfer Pak. (It was very useful at the time because we kept running out of batteries. Pokemania at its peak was crazy...)
Holy hell I completely forgot about this. Loved this and Blades of Steel. Heck I think me and my brothers spent more time brawling in that game than actually playing hockey, so maybe that counts?
In recent memory, easily Gwent from TW3. Feel like I played that even more than the actual game. LOL Avoiding the standalone beta... just want the final real deal.