With a million new games coming out all the time, and new consoles on the way...I just don't understand people wanting to replay old, dusty PS1 games anymore.
I still fire up games like Super Mario Bros 3/World/Yoshi's Island, Castlevania 3, Contra, Link to the Past, Flashback, etc, etc, despite having played those back in the 80's and 90's on their respective systems, because those games are fun and hold up.
There are more than a few games in the PS1 library that hold up incredibly well (ie, the FF games, Chrono Trigger/Cross, Vandal Hearts, Vagrant Story, FF Tactics, Castlevania: SOTN, etc, etc).
I got to play with the PS1 emulator on the Vita at E3 this year, and,
1) It still seemed pretty janky. Either that, or Tomb Raider: The Last Revelation is a lot worse than I remember (I think it's a combination of the two). The controls seemed off, and the performance was questionable. At least for Tomb Raider. The buttons were also configured for Japanese (O to confirm, X to cancel, etc). Settings were disabled, so I couldn't adjust anything.
2) Final Fantasy VII looked really, really good on that 5" screen. It was only displaying at 4:3 aspect ratio, but I was surprised at how nice it looks, so I can't imagine how fantastic some of the 2D games and games like FFIX and Chrono Cross are going to look.
Some game play is just universal and transcends console generations.
Many of us are playing these games for the first time as well (never played Alundra beyond the first dungeon, or Tomba, or Vagrant Story, etc).
Some of us just want to replay our favorites on the go (ie, I'm dying to replay Chrono Cross, and I have a long bus ride to and from work in the mornings).