I like OP's way of thinking.
With that said, I like all Generations of Pokemon, and Gen 5 is quite possibly my favorite in terms of the quality of the gameplay and the openness of exploration. Unova had a ton of secrets in BW1. It's surprising how non-linear it actually is overall, compared to older Generations that offered a more diversely laid out region yet had less exploration. After all, the exploration and Variety are what makes the single-player Pokemon experience for me.
Playing Generation I games even today though has a feel that modern Pokémon just doesn't. Is Gen I as GOOD in terms of quality, storytelling, and polish as today's Pokémon games? Certainly not. But Generations I and II, I think, have a special charm that can be attributed entirely to the hardware limitations of the Game Boy. The Graphics weren't fancy, detailed and beautiful, but simple and charming. I still love Generation II's tileset and sprites just because of the feel the gave the game, and the GameBoy music perfected the experience in it's own, imperfect way.
In short, Gen I and II were good for being not as good, and current Generations are good for being better designed in terms of gameplay. That's what I think. The old games also stand quite well for me just because of my fascination with some of the strange workarounds and odd coding techniques that resulted in some of the infamous glitches and glitch Pokemon in Generation I.