EXACTLY!
i agree
but your misunderstanding my post
i'm not saying that Halo is good because alot of people like it.
wut i'm saying is that Just because he thinks it sucks doesn't mean it actually sucks. if he had said "Halo sucks in my opinion" then i wouldn't have replied to him 
But, in all seriousness, isn't that pretty much a given? It kinda annoys me nowadays how, when you want to state something you believe, your opinion, you have to outright say, "In my opinion....". Back in the day it was never like that. When someone said, "Man, this game is the worst game ever!", just that alone was enough for people to understand that it was an opinion. We never used to make use with a constant barrage of "Oh, but it's YOUR opinion!" or "It's not fact, just opinion!". It would be like stating everything you do before you do it. "I am putting my plate of food on the table! I am taking a bite! I am chewing my food!".
But yeah, other than that, I do agree. Popularity =/= something being good(Twilight...erg), but everybody's entitled to like what they want to like.