For some odd reason as a throwback to Kanto, the writers had Ash capture over 10 Pokemon in BW. Whereas in AG Ash only captured 5 Pokemon, in DP he only captured 6, and now in XY his capture rate is looking very similar to those two series.
Yet in BW Ash caught 10 pokemon. Given BW was also faster paced and moved through the Gyms quickly, Ash's Pokemon didn't have much time for development. The following filler island saga after the league didn't help matters.
Unova is the only saga since Johto where Ash doesn't have a fully evolved starter, and its also the only saga where he got all 3 starters again. Coincidence? I think not. The rest of his captures also didn't even do all that much.
What do you think?