I'm going to keep this short and sweet. Between Yellow, Crystal, Emerald, Platinum, and USUM which "third game" do you feel was more polished than the rest? Which one did you have the best experiences with? I included B2W2 here anyway because even though it's not a third game, I feel people would still want to include it anyway since it's the only sequel to date so I might as well include it in something. :x
I really like the way B2W2 had such an amazing idea to play off the original games as a sequel and that is what I was hoping would be the trend. It made an interesting plot and it showed the consequences of the protagonists actions in a way since we just defeated the boss, not arrested those who were involved.
Black 2 / White 2... Because I'm very fond of airships powered by my favourite frosty lizard. Other than that I think I like Emerald a lot too, the Battle Frontier was so much fun!
Poor Pikachu... the original walk-behind-you Pokémon is all but forgotten. XD For me, Emerald is the definition of a 'complete' Pokémon game.
Technically I know that BW2 is the best in terms of changes made, but I'm still salty about a certain event that made me quit the game. So I say Platinum.
Gotta say it's a tie between Platinum and Emerald for me, but if I had to pick one, it's Platinum. I know people are tired of hearing about it these days, but Plat's Battle Frontier really made it one of the best Pokémon games ever, imo.
I gotta say BW2 because it caught me off guard when it first came out. I was quite invested in BW's storyline at that time and like many others, expected something like a "Gray" version but surprise surprise, they actually made a story sequel to BW! Imagine how happy it made little ol' me But in terms of post-game content, I would say Emerald because it had so much additional content and gives you a reason to carefully raise your 'mons.
I thought this was going to be about the fact that an actual "third" game (opposed to third-and-fourth) hasn't been made in almost ten years. *angry sigh* I'm still super, super, super angry about there being no Pokémon Z. Out of this entire list, I only have Black 2 and Ultra Sun, and out of those, I never actually played the either of the first pair of the respective gens, so I can't adequately compare the improvements of, well, any third game. I either played only the original pair or only the sequel pair. Although I don't like Pikachu at all, I'm going to have to vote Yellow. It introduced follower Pokémon (which is one of my favorite features of HG/SS, which is my favorite Pokémon games), and laid the initial groundwork of "we don't have to just make a cash grab out of selling to version of the same game, but can actually improve upon it before moving onto another project!". If it wasn't for yellow initiating that train of though, the overall improvement of the series as a whole may have been a lot slower.
In terms of best experience was B2W2, but in terms of which one I remember the most fondly was platinum. That game is special to me because it got me back into Pokémon.
Since we're counting BW2 I'll have to say them, they far exceeded my expatiation for them and I really just love the story overall.
Like some others I remember Platinum the most fondly. I think it added the best improvements and polished all the flaws DP had. Plus, it upped the difficulty, the graphics were great, it was overall a wonderful game! BW2 is a very close second, though. I absolutely loved it, I loved the new Pokédex, new towns and gym leaders, and how dark it felt. It truly was an amazing game.
As much as I loved gen 4, I don't feel like Platinum was different enough from the original games. I remember Diamond more fondly. So I gotta give it to black 2 and white 2. I haven't played the games myself but I have seen let's plays of them and I really feel like they are the example of what a third game should be: Same region, but a different story set after the first games.
I've only played Yellow and Crystal as far as 'third games' go. I like Yellow the best, partially because of the memories I have of playing it during my early days of doing the main Pokémon games. As for Crystal, I'm not all that fond of it other than it having the ability to play as a girl (which I only did just to take advantage of said feature). The biggest thing about it that turns me off is that you can't get an Electric-type in the wild until much later in the game than most other main series games (due to the boneheaded decision to remove Mareep).