Well considering most of the other games added a crap ton of basically rehashes with "pre evos" and babies and all that stuff . . I think Mega's are just as eligible for counting as another generation. If you took out a lot of the fluff of the other generations the real pokemon count would be pretty similar. I think the Megas add enough strategic depth to make up for only 69 real pokemon.
But they aren't actually new Pokemon they're just new forms of them.
No they are evolutions it's even in their name. They are a new type of evolution method yes, but they are evolutions none the less. The only true difference you have is one is temporary but the trade off is that for being temporary they were able to be made much stronger.
It's basically the line between a new form and a new evolution, it fits into both and is the way this generation chose to give new evolutions to old pokemon but not deal with all the whinning of how their old pokemon had been tainted.
I've got a quote that embodies you perfectly, but it's seventy-three posts long, has a few massive flowcharts, and lots of Xion-KMA to Me