Im talking about the sinnoh games here:
Well the music was awesome, especially with Sinnoh's jazz influence.
The Pokemon? Ehh.
Some I loved (Glaceon <3<3<3), but ones like Pachirisu, Shellos*, and Krikitot (Defiantly spelling that wrong) were just bad IMO.
Also, there were too many old 'mons popping up everywhere, and too many evolutions to old 'mons.
I remember reading a review or something where someone said "I don't mind seeing old pokemon, just not right when I start the game", which I totally agree with.
* Fun fact: Shellos was actually going to be released in RSE.
Which is probably why it seems more like 3rd gen Pokemon (if that makes sense).