I want to say 4 because that’s the one I started with but, realistically, gen 5 was the best. It had so many features:

• Animated sprites (they look better than the 3d models and I’ll never get over it)
• An actual story
• Used only the new pokemon for the regional dex
• Very cool abilities like Zoroarks

This is as much a meme as those minions post you see in Facebook

Any server federated with them is unusable as far as I’m concerned.