We're gonna get into a philosophical debate now.
Quality is objective. Compare Big Rigs Over the Road Racing to Need for Speed Underground, released the same year, and it's black and white which is the better game. Big Rigs is inherently inferior to Need for Speed, personal opinion removed.
And if two such diametrically opposed titles can be objectively different in quality, then it stands to reason two titles of similar quality can still be objectively rated against each other.
Personal enjoyment of a title is subjective, true, but the best game and movie reviews attempt to remove as much personal bias from the equation as possible. It's why Roger Ebert was so highly regarded. On many different occasions he'd rave about movies he'd give low ratings, and confess boredom at ones he'd give high ones. Because he'd rate a title objectively, and then give his subjective opinion of the film.
In fact, I think it shows a high level of arrogance for someone to play a game, hate it, and then declare it bad. It's very easy to enjoy a bug ridden mess and not enjoy a masterpiece. First person shooters do nothing for me; I've never played one I particularly enjoyed. I'd play a crappy NES platformer over the next big FPS game any day of the week. But it's still easy to look at what I'm playing, and look at what they're playing, and say, yeah, you know what, I'm the one playing the terrible game.
