TR2 is hailed as the pinnacle of the original series. My vote is loyal to TR2 as I've beaten it countless times. I have it digitally on PSN, physically as a PSOne disk and I own both a physical and digital copy of it for the PC. I love that game. I own all the TR games though.
I went with Legend. It has what I feel is a better base system for some of the platforming puzzles, you don't get any sort of overpowered crap until literally the very finale of the game, and it was fairly interesting. Underworld was good too, but once you get Mjolnir, the entire game is a cakewalk.