I LIKE the 2D sprites and gameplay. I don't like the 3DS THAT much and its like they got to make everything 3D. Take Fire Emblem: Awakening for example. Fire Emblem has been awesome for the other consoles but now it's 3D and annoying.
I think I have both proven my point and made a lasting affect on your opinion of Pokemon on the 3DS.
1. I have not played Colosseum or Battle Revolution. I have played Pokemon Snap and Hey You Pikachu! and Stadium. They don't really count though and on top of that all the 2D Pokemon games were better.
2. I think people don't like Colosseum or Battle Revolution that much anyway. Its better to keep 3D Pokemon to home consoles anyway.
1. That's like saying you prefer side-scrolling Mario games to 3D ones after only playing Mario Party.
2. Battle Revolution didn't have any story and you need to rely on your DP games to do well, so that's no competition. I feel like if people don't like XD or Colosseum it's because it wasn't free roaming and you had set Pokemon you could catch. The first one restricted you do about 50, while the second 70. Colosseum got amazing reviews, if I remember correctly.
The 3D should only affect the visuals, not so much the gameplay. As long as they leave the main goal being getting 8 badges and beating the E4, while keeping the same type of free roaming world, it should be like any other Pokemon game. They battles may be slower, that being said, but that's still only aesthetic change.