Why would buying old games be pointless? The only disadvantage old games have over newer games are the graphics, and, frankly, I think all the people that come and register to this kind of site have long agreed that graphics aren't all that important. Maybe some design philosophies were different back then (Not neccesarily worse. Cover based shooting wasn't around, though that may be considered a negative by most, it's a big positive for me), maybe some common things that we take for granted were done worse (Aiming with the keyboard on some games such as Bungie's "Marathon"), but those games are were todays games come from, and some of them are in the honored position of "GREATEST GAME OF ALL TIME" for many.
Put it this way: People today who don't buy older games won't play Deus Ex 1, the System Shocks... Heck, even the Half-Lifes (In my opinion, the best series of all time) might be considered "Old games". Believe me, I'm no "Retro gamer" nor do I fondly look back at the "Good old times" when the best graphics were 8-bit, but I will say this over and over: Plenty of games as far back as the Atari 2600 were excellent, and you're loosing out if you don't play them.
Also, the fall in prices makes it even triple worth it. If I remember right you could buy 10 copies of Deus Ex for what Skyrim (An equally excellent game) is worth on Steam (That is, taking the Steam price of both games).