With some Excel magic, I have come up with this tally! These are the tallies of Pokemon in the Kalos Pokedex, grouped by their region of origin:
Kanto: 111 (24.2%)
Johto: 63 (13.7%)
Hoenn: 79 (17.2%)
Sinnoh: 52 (11.3%)
Unova: 80 (17.5%)
Kalos: 72 (15.7%)
Total: 457 (100%)
And this total number is verified by Bulbapedia (in the Trivia section), so Excel counted everything correctly.
Your observation proves to be true: apart from the Kanto, Kalos is mostly habited by Hoenn- and Unova-based Pokemon.
Other random statistics; the Kalos Pokedex consists of...
73.5% of all Kanto Pokemon (111/151).
42% of all Johto Pokemon (63/150).
58.5% of all Hoenn Pokemon (79/135).
48.5% of all Sinnoh Pokemon (52/107).
51.2% of all Unova Pokemon (80/156).
100% of all Kalos Pokemon (surprisingly, 72/72).
Hope I helped. :)
Source: Above link