I've only read the thread to page 3, keep that in mind if someone has said this before me.
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Lots of the problem lies in the misunderstanding of hardcore and casual gamers, in some ways. As far as I'm concerned, any CoD-fanboy is a casual gamer now, simply because of the lack of depth he/she has when he/she looks at the game. They don't care for balanced gaming (i.e. Not ONLY PvP-based leveling. It hasn't worked before, it won't work now, STOP THIS.) or fun anymore, it seems, but for the bragging rights.
I notice this even more when listening to their conversations about their online matches with each other or with some 'noob' that kept 'noob tubing' them. What? How is using what the game gives you wrong?
Now, I'm not pro-MMOFPS, because of the lack of PvE (mostly), as mentioned above. This makes it frustrating to get to the point where you feel satisfied with how you're scoring and such (multiplayer is mostly about having fun winning, and there's nothing wrong in that as long as it's in teams, if you ask me), yet even then it's minor, I'd believe, as you're left with the knowledge that the only reason you're winning is because you've got better weapons than "dat ubnub that naded ppl."
I know, I'm getting into the same thing. Commenting other peoples' fun. But I still think the concept of a levelling-system being purely PvP-based is ridiculously stupid. Please, AAA-industry, make games that are fun again, without the only reason for this fun being the knowledge that someone else didn't have fun. Please. Don't make "multiplayer gaming" and "griefing" synonyms.