The Pokémon Stadium games have been very mixed. In a way for their time getting to see your favorite Pokémon in 3D on your N64 was one of the coolest things. At the same time, Pokémon Stadium took out one of the best things about Pokémon: exploring the world and catching Pokémon. The first one was released in Japan in 1998 and had only 42 Pokémon. The second one, called simply Pokémon Stadium in the US, was released in 1999. Considering it has taken 14 years for a main series game with 3D Pokémon in battle, this is pretty impressive.
For me, Pokémon Stadium was a lot of fun. When I was a kid I really enjoyed the mini games with friends, even though I was too young to realize they really weren’t very good. Gym Leader Tower, where you would go to participate in battles against trainers and ultimately the Gym Leaders, was pretty fun too, because you could pick a team of rentals and it was actually pretty hard. This, along with the Tournaments, got old pretty quickly though. The thing that was cool about Pokémon Stadium though was that you could battle your friends with rental Pokémon, instead of having to train a real team of Pokémon in the main series games. If you wanted though you could transfer Pokémon from Red, Blue or Yellow to give yourself an advantage.
One of the coolest things though was the ability to play Pokémon Red, Blue or Yellow on the big screen, if you had a gameboy player for the N64. Pokémon Stadium 2 did the same thing with Gold/Silver/Crystal. On top of this though, from what I’ve heard (I haven’t done it yet) if you beat the Poké Cup or the Prime Cup, you unlock “Doduo Mode” which allows you to play the cartridge games in double speed. If you defeat both, you unlock “Dodrio Mode” which lets you play them at triple speed. So if you want to collect them all or train a powerful team a lot faster, this is a huge boon.
There have been several Pokémon Stadium-like games, with one of the more recent ones being Pokémon Battle Revolution. This is probably closest to the older ones, but they took out something that made the originals great: Rentals. You can’t rent Pokémon, you can either use the set they give you (and switch out Pokémon if you beat people, it says, but I never figured this out) or transfer Pokémon from Diamond/Pearl/Platinum. So basically, if you only have Pokémon Battle Revolution and none of the DS games, you’re not going to have much fun with it. You can only battle your friends if they also have a team on a DS game too. If you do this though the graphics look great and it’s still pretty fun.