Warning: You will be disappointed. This is inevitable. Whether you are springing for a classic you've never tried, or a much loved game from when you were younger, the reality is not going to meet your expectations. So, remember that these games were made around 15 years ago, and lower your expectations accordingly.
Having said that, I bought Crash 3 for PS3 fairly recently after owning it on PS1, and despite how outdated it is, I've enjoyed it a great deal, so I recommend going for that.
EDIT: I should point out that Metal Gear Solid is very widely loved, but I honestly found it unplayable, it was so dated. And stay the hell away from Syphon Filter, especially if you've ever liked it in the past.
(Former) Lead Moderator and (Eternal) VGC Detective 
