I didn't like Gen 4 and 5 as much as I thought I would. I literally ditched the game after a few hours of gameplay beyond the Elite 4. I didn't even bother with buying BW2 or Platinum for that matter. My average game time can't even surpass 60-70 Hours anymore.
Gen 5 was bland to me honestly. The series has been growing stagnant but Gen 5 was the first time I felt it actually took a step back. I liked only a small handful of Gen 5 Pokemon, disliked the C-gear, the evil organization, characters and the region as well. I have had friends that felt similiar but who stuck it out and eventually it grew on them but to me it just felt very bland and I had other games in my backlog to get through so I decided to set it aside and skipped B2/W2 altogether.
From what I've seen of X and Y it looks as if I'm finally getting an installment that I can legitimately feel excited about. The Gen 6 Pokemon have been a higher quality design wise than most of gen 5 IMO and the Mega evos have retained the charm of the original Pokemon quite well (I wish Magmortar, Ryperior, etc had accomplished the same).
tldr: Didn't give gen 5 a fair shake. Thought it was bland. Gen 6 looks excellent.
I love it when other people save me the trouble of writing my own opinion out myself :)