This is such an overdone argument that I don't even know why I bother to respond.
My first Pokemon game was blue when I was five years old. I've played Silver and Sapphire, took a break during Pearl/Diamond/Platinum and returned with Black. And 5 is my favorite gen because it's number and that it wasn't bogged down with shoving old Pokemon in your face. I don't care about catching Pikachu and even with my "old favourites" I already had ample chance to catcha nd use them in older games. Ninetales was my first favourite Pokemon, but I haven't used it since Silver because...why? Why use the same character over and over again? Alola is the first time since Johto I'm having a Ninetales on my team again because of the Alolan Form.
I also loved the designs. In my eyes each generation has improved the designs, another reason why I am kind disappointing that the last two gens were small; we only got less than hundred excellently designed Alola and Kalos mon each, but we have 150 often rather bland Kanto mons from the time when Sugimori only had access to 12 watercolors and "Three Diglets next to each other" counted as an evolution. yay.
I don't know if this is a minority opinion, but I definitely feel the same way 100% about the Generation V Pokémon: My "old favorites" can wait until I'm done with the game. From an artistic standpoint, there are also plenty of Generation V Pokémon I really like, like the Darumaka line, the Cottonnee line, the Petilil line, the Golett line, the Scraggy line, the Joltik line, the Solosis line, the Elgyem line, etc. (Some are on the conceptual level though--I like what they did with water bears for the Solosis line--it's about time we had a Pokémon themed on a microorganism.) And from a gameplay perspective, there was a sense of newness and discovery in
Pokémon Black and White I hadn't felt in a long time. And I had so many ideas about what to put on my team that I spent hours trying to decide what would stay and what would go. It was glorious.
For me, a major reason I'm playing a new generation of Pokémon games is to experience and use the new Pokémon. Personally, there is little reason for me to use a Pokémon I had already used before (unless I like it that much, but there are very few Pokémon that fulfill that role). It's why I'm always disappointed in seeing generations past V be pretty small.
I can understand it though: Generation V had the fewest standout Pokémon of any generation in proportion to size. Pokémon people took a real liking to during its own time, like Durant and Keldeo, seem to have since all fallen by the wayside the moment
X and Y came out. Perhaps to other people, new Pokémon stand out more when placed in a crowd of old Pokémon. Dhelmise stands out more if mixed in with larger quantities of Magikarps and Wailmers than if it was just itself and Wishiwashi, for instance. But me, old Pokémon feel like filler. Been there, done that.