Did an event occur which lead to you looking at a Pokemon differently than before? For example, I had a close friend who really liked Azumarill, but now we're not friends anymore and I see bitterness when I look at Azumarill.
When I was little I had pokemon cards, I let my brother use some of my cards granted he DID NOT ante my Tangela. He did. And he lost. Now, that didn't change anything about how much I <3 Tangela, but, one of my friends gave me a charizard, and another gave me a Charmander and Charmeleon. They are easily my favorite starters, and some of my favorite pokemon now. I still hate my brother for losing my Tangela.
After seeing Giovanni's Beedrill kick Lance's Dragon pokemon's butts in the manga, I think it's one of the most badass pokemon ever. Through the manga I also learned to appreciate underrated pokemon like Raticate and Doduo more.
Ooh, I forgot, which I probably shouldn't have. I used to have a dog that looked very similar to Granbull, so I make it tradition in each game to get myself a Male Granbull and name it after my dog. Then I use it for contests etc, so he's gonna be a movie star this time around by the looks of it. I'm sad, I know, but I never really gave much thought to Granbull before my dog died. Still need to get one for B2. >.<
I didn't like the Roggengola line from the start, but when I began using one and saw that it had potential to be on my team as pretty much a powerhouse, I began to use it. ^_^ Now I like it :3 seeing Ash get a Roggengola in the anime as well and using it in battle is cool Powerful ^_^