Why I like retro? Well I come from a time where they weren't retro
Compare it to music; people nowadays still listen to music from the 60's, 70's, etc. There are also people like me who listen primarily to music from that era even though I wasn't even born yet then; I acknowledge the passion and the honesty in the music made then. Likewise there are also young gamers who reach back to the games of ye olde days for the same reasons, possibly with a little encouragement from dear old dad.
But that is still a minority. I see a tendency among current generation gamers where they state that old = bad
, and old can be as little as 2 years. I don't think you'd easily convince someone to give Gears of War 1 another playthrough even if it is only a few years old and available for the still current X-Box 360! Why would you? There is Gears of War 3...
I'd say that to be a true retro gamer, you simply have a more open mind. Old = not necessarily bad (because granted, there are a number of games that didn't age well at all). You play those games maybe because you have fond memories of it, you want a trip down nostalgia lane or you want to experience what the genius game designers of those days cooked up with the limited means at their disposal.
Or you play them to be inspired. Because games are apparently also comparable to fashion; if you look at the current generation of independent developers, they mostly focus on bringing the retro feel back to the games they make today. Partly out of necessity, because that is within budget and capabilities. But they actually manage to take the ideas of 20 years ago, apply it to a modern market and do very well with it.
So in that respect, can games really become retro games? I think not, they are timeless.