Surprised this masterpiece hasn't been mentioned yet:
But anyway, honestly my favorite generation with my favorite games being BW2. There is just so much to be appreciated about this generation. This'll probably just turn into a gushing rant but here goes. Immediately what stands out for me in gen 5 is the sheer amount of effort that seemingly went into these games. From creating an entirely new roster of Pokemon to traverse the region with to the sheer amount of content in these games, there's so much to love about this generation.
Of course, it goes without saying, this was the first generation with a proper storyline and actual characters. Whether or not that's needed in a Pokemon game is another question but what resonated with me was that Gamefreak addressed the moral concerns of Pokemon battling which was a very bold move considering the franchise is arguably primarily based around this. It could have gone a little further in my opinion as we never really got a solid answer. I guess the point was to leave it up to the player as to whether they agreed with capturing and battling Pokemon or not but I'm not surprised the idea was never brought up again because it would be hard to justify making more games if they explicitly said it was wrong. Regardless, getting a little off topic here, I really admired how the developers were brave enough to consciously implement the moral concerns of the franchise within the games.
As for the region itself, people always Unova is too linear which I can see, but just look at the map of Black and White 2 (sorry for the bad quality image):
There's so many extra areas to go back to and explore, some of which are only accessible in certain seasons. The layout, colours and even music of the routes changing with the seasons is just a genius idea. The route designs themselves in this region are also simply phenomenal and are not at all linear.
The music, which I've alluded to at the top of this post is also in my opinion some of the best and most consistent in the series. I can't really point to a single piece of music that I don't like in Unova. On top of this, the music itself changes with different instruments dipping in and out depending on the seasons as I've stated above, but each gym also has unique music as well. And the low hp music? Annoying after a while but another small touch that highlights the thought and effort that went into this generation. Speaking of, the gym leaders themselves actually play an active role in the politics and events of the region instead of being these all powerful trainers that just sit there and watch as the world burns around them. The scene in Black and White where all the gym leaders turn up at the Pokemon League is the culmination of this and is just an awesome moment.
And how could I not mention the animated sprites? The fact that they gave the go ahead to animate EVERY SINGLE POKEMON in a way that emphasises the unique character of each Pokemon is just baffling to me considering the comparatively little effort that has been put into Pokemon games since. The amount of time and effort that it took to animate every Pokemon, and on the DS might I add, must have been pretty insane. The fact that they perfectly captured exactly how you would expect each Pokemon to move and express itself is an absolute marvel considering the limited technology even if it was quite cutting edge at the time. Graphics aren't everything as they say but the aesthetic and art style employed by these games is outstanding and it still looks great to this day. Probably still the most aestehtically pleasing Pokemon games to this day if you ask me. I just find the games' aesthetic so charming. Admittedly some of the new Pokemon designs themselves really miss but the ones that hit, absolutely slap with some of the best designs to date. Big up the bug types of this region.
Need I also mention on the theme of effort, Gamefreak actually made an attempt to genuinly distinguish the two versions of both games in this generation enough to actually give you a reason to buy both outside of the need to simply catch them all. Route 4, Black City, White Forest, Resversal Mountain, Opelucid City, the list goes on. The fact that they gave you an actual incentive to attempt and stick with the tough post-game battle facilities by gifting you a shiny Dratini in White 2 and a shiny Gible in Black 2 instead of, you win, here's a medal, was an great idea. My brother got White 2 and I got Black 2 which made me really jealous that he got to recieve a shiny that was actually distinguishable from it's normal colours. On the subject of battle facilities, not only did we get White Treehollow and Black Tower, but we also got the Battle Subway AND the masterpiece that is the Pokemon World Tournament. The PWT felt like some real anime type tournament and was a fantastic culimination of all the strongest trainers we've met so far on our Pokemon journey. Just the perfect idea for a battle facility and arguably the tournament type format that the gym and elite four challenge should be (I think this is somewhat similar to the idea behind the gym challenge in SwSh but I've not played those games so I don't know).
Lastly, we move onto the Entralink. Perhaps many of you never interatced with or missed out on this feature, but it was an absolute blast if you had someone else to play with (in my case, my brother). The little challenges and games modes you could participate in (funfest missions in particular) were extremely fun and against the clock if I remember correctly. Charging around the region with your pals in a bid to collect items and objects was honestly so exciting to me and I'm sad it's a feature it seems like not many got to experience.
Honestly, I could go on forever about this generation and I'm sure there's still so many great features I've not covered. I really do believe BW2 in particular is the pinnacle of Pokemon but I'll leave it here for now before I get too carried away.