I enjoyed them, but I don't think they added enough to the material, other than the Sevii Islands. I played LeafGreen, and I felt like I was playing the EXACT same game, with updated mechanics and remastered graphics. They also didn't add enough additional legendaries, with the only ones being The Dog Trio of Johto. They could have at least added a big island reminiscent of Mt. Silver, with a massive legendary Pokemon, probably Ho-Oh and Lugia, for FireRed and LeafGreen, respectively.
Speaking of those rascals, you could never complete your Pokedex unless you went to a wretched event where you could DOWNLOAD the on your game. DOWNLOAD. This necessarily means that unless you went to one of those damned events, or you cheated (which is never condoned by Nintendo), you had absolutely no hope in completing your Pokedex. A minor personal complaint is the lack of animated sprites in these and RS. Crystal had this all set up, but they took until Emerald to redo this.
I'm not all complaints, though. It was great to replay the games that kept me captivated as a child, and I somewhat liked the new key items, like the Fame Checker, which I could never complete, but oh, well. The addition of abilities was a blessing and a curse for certain Pokemon, like Koffing, which could now evade Ground moves. The music was not stellar, but it was pretty acceptable.
Overall, I enjoyed this game, but I feel that it could have been reinforced more by Gamefreak.