Welcome to Gaia! ::

Here's just a few that come to mind off the top of my head that I noticed you missed.

Snap
+ Utilized the Snap Stations to print out the pictures you take on the game.
- The Snap Stations cost money and were only at Blockbuster... and fizzled. And who would pay for those pics anyway?

Gold/Silver
+ Extremely rare and hard to find Shining Pokemon, which are colored differently from their counterparts.
+ A helpful but extremely rare virus called the PokeRus to help improve training.

Crystal
+ The Move Tutor teaches your Pokemon some moves for a hefty price in Game Corner Coins, but they're versatile moves, so it's good.

Ruby/Sapphire
+ Record Mixing and watching the terrible, terrible names your friends give their Pokemon is entertaining and creative.
+ 4 players can battle at once when linked up. Same goes for contests.
- No backward compatibility with older versions. (Although, if you understood how the new mechanics work, you'd see it was for the better.)

Colosseum
- No Minigames to play.
- No boxed Pokemon management like in Stadium 2. (Nintendo will lure you into buying Pokemon Box for that.)

FireRed/LeafGreen
+ Move Tutors return so you can teach your Pokemon freaky moves. Only once per game, so they're like TMs.
- Chansey is no longer in the Unknown Dungeon, and now you have to catch the little !@#$ in the Safari Zone. Have fun trying to catch one!

Emerald
+ More Move Tutors for even stranger moves!

Steven plays the roll of Red!? I didn't know that...

Smeargle was in gold and silver.