It introduced some of my favorite gems like Galvantula, Haxorus, Scrafty, etc. Honestly the only Unova Pokemon I really don't like from it is Ferrothorn. I even used it in a Nuzlocke trying to like it more, but it never grew on me and I hate seeing it in competitive play. =/
The first games where one of my favorites and the second games made it even better. The only thing I didn't like about gen 5 honestly was the disappointing bottom screen in comparison to its gen 4 predecessors.
Imagine giving a child 100 new toys but he throws a tantrum because 5 or 6 of them he doesn't like the look of. This is also known as the Pokemon fanbase.