I guess if you like monotony, then sure video games are better now than they were in the past. Everything is either a First Person Shooter or a 3D platform game these days. Where are the side scrollers? Where are the vertical space shooters? Just because graphics are 3D these days doesn't mean that they can't be played on a 2 dimensional plane. Take Castlevania: Symphony of the Night for example. The game was incredible, and widely acknowledged as the best Castlevania game to date. And it was a 2D game on PlayStation, well after 3D graphics became mainstream.
I'm not saying 3D graphics don't have their place, but I am saying that they aren't necessary for a great game. The once-awesome Mega Man series took a drastic plunge when it went 3D. On the flip-side, Capcom's fighting games have remained 2D and continued to prove both enjoyable and successful. Their one attempt at 3D (Street Fighter EX) was a train wreck, and they haven't tried since.
Why do we play games? Well, I guess the answers will vary on that question. But I know that I play them for fun. Regardless of how good a game LOOKS, if there's a game that has worse graphics but is more fun to play, I'm going to play that one.
Oh, and sales don't mean squat. Just because so many people bought it doesn't mean its not trash. I have bought a lot of games in the past that turned out to be terrible, yet my purchase would be added into sales numbers.
I'm simply saying that gamers these days rarely get to see what a GOOD game is all about. You want a good game? Go find yourself a copy of the original Punch Out for NES. Final Fantasy III and Chrono Trigger for SNES. Mega Man 2 for NES. The original Legend of Zelda on NES. Zelda 3 on SNES. Castlevania: Symphony of the Night on PlayStation. There are many more, but these are prime examples of games that are tons of fun yet aren't graphically amazing (they were back when they were released, but not anymore of course).
Again, I'm not saying that good games don't exist today. I've been playing a lot of Knights of the Old Republic II lately, I love every Final Fantasy, I love the Metroid Prime series, I can't wait for the next Metal Gear Solid, and I paused Halo 2 to type this. But this thread is entitled the "Best Game Ever," and I don't feel that any of the games from the current generation can claim that titled (though some come close).
Oh, and by the way, this is all my opinion. Never said you had to agree.