Personally, I don't mind that Kalos introduced less Pokemon. We've already had a gen where absolutely no old Pokemon showed up until post game in the first two games, and that was fun in its own way. It was nice to have to re-learn everything all over again.
In this game, however, I felt that everything got an update, whether it was superficial (merely transitioning the Pokemon to 3D and refining their cries), or not (MEGA PINSIR!!!!!!
), and this made all the old Pokemon feel fresh and new again. With them alongside the native Kalos Pokemon, I honestly felt spoiled for choice in terms of trying something "new". Using Aerodactyl felt every bit as new to me as using Goodra not only because I'd never really used one in previous generations, but also because the thing got turned into an absolute killer with Mega evolution. Using Venusaur, even apart from its mega evolution, was a new experience too because now with the new Kalos Pokemon, moves, and abilities, it seemed like there was a ton of new strategies to try that I had never thought of before. There's so many Pokemon I want to try, both new and old, because they all have something new to offer.
The net result is that I, personally, don't feel that there's any lack of "new" Pokemon. Even though only 60-some-odd of them are truly new (i.e., not mega-evolutions or otherwise related to previously existing Pokemon), the amount of content in the game more than makes up for it to the point where I don't notice that there aren't many Kalos Pokemon until someone points it out to me. x)