As soon as I saw the words "So was this generation just…" in the "Last Post" bit, I immediately face-palmed. I just ranted about this on Twitter, but no. This generation is NOT filler. You know, I read somewhere that BW were "just something they were making in-between XY". Despite that, there is more that this generation did than just that.
As a lot of people have already said, there is a lot that Generation V introduced, like reusable TMs, which makes it nowhere near as much of a chore to try to get important moves for Pokémon (no more having to spend hours grinding in the Battle Frontier for an Earthquake TM!). And Hidden Abilities, also. These abilities really changed the ways that a LOT of Pokémon were used competitively, like Dragonite, Ninetales and a lot of other Pokémon that before were barely usable at all.
Also, do you know what else BW does that it's the only main series game to do so far? Look at the end of the game. Not only do they stem on a different route from having you simply become the Champion, but the final battles actually throw a trainer controlled legendary at you. Granted, XD Gale of Darkness has done that, and so have the Master Battles in PBR, but we're talking main series here. As been mentioned, the game actually wants to make you think that training Pokémon is wrong, even though ultimately Ghetsis wanted to make Pokémon illegal for everyone but himself. That twist at the end really made for a grand ending that's original and different.
As for Black 2 and White 2? I have talked about these games countless times. They are still my favorites in the series. While they traded the different approach for the "same" formula the series has always went by, I use the term "same" very loosely, because granted you're following a similar path but they did enhance it. It's not just "the same game as the previous adventure" like Emerald and Platinum (although Platinum fixes some major issues with DP) - they're actually continuing the story and making it different. In addition to that, for the time, they had more Pokémon to find in-game than any other. It also introduced actually decent rewards for Pokédex completion, like the Oval Charm and Shiny Charm. You also have the fact that Ghetsis does something that no other villain in the main series has done so far: actually attempt to kill/physically harm you, by trying to have Kyurem use Glaciate on you. And they had some neat version exclusive areas (like differences between Route 4, Reversal Mountain, the Plasma Frigate and Victory Road), the most important one being the trainer marathon Black Tower/White Treehollow, so they actually make it different between them.
I won't talk too much about the PWT, but even if some people think that wasn't ideal, it did allow for some nice visits from past Gym Leaders. And like Emerald, a previous Gym Leader becomes a new Champion, but unlike Wallace, Iris actually gets some backstory to her thanks to the Memory Link (which I didn't mention above, but it's also something kinda neat). Her battle intro also has full body art for both you and her before it begins, which is the only battle in the DS era, or any pre-XY game, to do that.
So no, I will never, EVER call Generation V filler. It did a lot for the series, and while XY may have expanded on the things that were new here, some of them aren't even present at all. Just my take on this matter.
