Depends on the game, really. Some 2D games rock and some 3D games rock, as some of both suck. You can't determine the worth of the game by whether it's 2D or 3D. So, I chose "both" because this isn't even a factor for me.
There has long been a debate over whether DOOM and other such games are 2D or 3D. To answer it, consider this: does it look 3D? Does it look like you're moving through a 3D environment? Yes? Okay then...it's 3D. The 3D techniques are simply inferior, as hardware was not capable at the time of utilizing proper 3D mathematics, so the closest approximation was used instead. It's not about the techniques used, it's about how the game appears. If it looks 3D, it is 3D. End of story.