Personally I was fortunate enough to watch half the episodes, scattered here and there, of the original and Johto series.
I liked Pokemon, but I was more hyped about Yugioh at the time, considering the characters actually progressed and became OP.
I missed the orange islands and Battle Frontier entirely, and only watched random parts of the AG and DP whenever I was bored and fortunate enough to catch Pokemon episodes on TV.
I don't even remember what episodes I watched back then, or my feelings towards them.
The only things I do remember are being put off by contests, which I thought was too girly at the time, and being extremely, yes, extremely upset at the departure of Misty.
Even at the age of 14, I shipped them really hard before I knew what shipping was. I actually turned off a lot of airing episodes of AG because I was so used to Misty, and her departure kind of ruined my interest. I regained some interested in DP with Dawn, and caught parts of the Sinnoh league.
BW started when I went to uni, and that's when I first had the chance to benefit from the *ahem* "limitless possibilities" of the internet.
By that point, I was completely turned off by Yugioh, which after watching a few episodes of GX and the stupid motorcycle stuff, I resolved to never watch it again (and I can proudly say that since grade 11 I haven't watched more than 30 seconds of it at a time). I still enjoyed the card game though.
Pokemon, on the other hand, had stayed steady with the same formula since the first time I watched it. I remember having so many unanswered questions about pokemon, and I saw many of my classmates playing pokemon. That got me even more curious, envious, and nostalgic. I remember being given pokemon cards such as Scyther and Zapdos, and they instantly became my favourites.
Soon I learned that I could play pokemon on my laptop, ahem ok I'll stop there...
Long story short, I got addicted to the game, and suddenly my nostalgia grew over 9000 and decided to catch up on the anime.
Since I could never follow it episode by episode in the past, I wasn't particularly bothered by the lack of continuity or progress on Ash's part.
(OK fine I admit, I was shocked that it lost to Snivy, but other than that I was OK with this recurring theme of resetting Ash's status.)
For the most part, I enjoyed BW but I didn't like Iris. She wasn't cute, and the only cute pokemon she had was Emolga. I was unimpressed with the battling, and upset at the lack of battle strategies, and most of all, upset at the lack of important wins throughout the whole freaking series. But I really liked the plot, Team Rocket's new demeanor, the frequent captures, Cynthia, Alder, and Meloetta. I thought the Unova Legendary Trio was ugly and crap compared to the Kanto/Johto Flying/4-legged Trios. I also thought Trip and Paul were the same person until I realized they weren't. Then I just thought Trip was terrible writing and a lazy copy of Paul, who I thought was just a copy of Gary.
Yeah I was pissed at the terrible writing at the Unova League, they should just have made Ash lose to Trip in the first round, I would have been happier with that result.
I was majorly disappointed with the lack of Charizard actually showing its full power. Pokemon activist N had to prevent Charizard from killing Dragonite, which was sad because I wanted Dragonite to die so badly, if it can't even beat a Krookodile it doesn't deserve to be called Dragonite, a pokemon I struggled so hard against in Pokemon Red. Plus I was butthurt that Iris got a free Dragonite despite being a no-skill loser. If she battled it, it would have swept her whole team without taking any damage.
But hey, I still enjoyed watching most of the episodes...
Until the Decolore Islands. Yeah about that...
I kept watching in desperate hope that should interesting would happen. Nope, nothing happened. So I decided that I would not watch XY.
Then XY came out. I didn't watch the first episode. But by that time I had started checking out these discussion forums.
All I saw were comments like holy miltank, its so good, awesome animation, 10/10...
So then I resolved to keep watching the anime, and I loved it for the most part since the beginning of XY.
Serena is cute, at first I was butthurt that Misty wasn't coming back and thought negatively about Amourshipping (cuz pokeshipping rulez all ^_^). Over time I softed up about it and now I am an amourshipper. I'm still sad about the lack of Mega Charizard Y, and the 6th/7th gyms being only 2v2, and Ramos and Valerie being weak.
But yeah I'm lovin this series and won't quit unless they really mess things up badly. That said, I believe viewership will increase significantly (back to early BW levels) if they provide strong continuity into Sun and Moon and a satisfying result at the Kalos League (top 2 or better). Otherwise, expect Sun and Moon to have even lower viewership than XY and the end of BW.