As a precursor to this topic, a bit about me: under almost all circumstances, I do my best to remain calm and collected; not a lot will bother me on-the-spot. When I'm gaming, however...all bets are _off_. Expletives fly fast and furious (sometimes controllers do, too), rage is in quick and endless supply, and the whirlpool of self-denigration cycles faster, in perpetuity. You think your 'bathroom face' is scary? You have never seen my 'gaming face'. And with even the smallest modicum of luck, you never will - it comes out in multiplayer sessions, sure, but only in a limited form. No, I will not provide pictures or videos, so don't ask.
Part of what makes games as a medium great is the stunning breadth of experience they can provide. Laugh, cry, think, space-out...whatever you want to do, there is a game to help you. So many blockbuster AAA titles hang (nearly) their entirety on the multiplayer experience; see any recent ModernBattlefieldHalo: Gears of Ops 5. Sure, there's a cursory nod to a single player campaign, but let's be (superlatively) honest - nobody buys those games for the campaign. What a sad state of affairs - I would gladly lay down money for any of those titles, as I do genuinely enjoy an adequately-well-executed shooter, but frankly the cesspool of a community surrounding their ilk is enough to keep me away. And the afterthought that is single player just can't do enough to attract me. Incidentally, please prove me wrong and call me out if I'm being completely short-sighted on any of those points. (Five-hour, over-checkpointing, cover-hugging fests do not count, so don't bother bringing those up - you know exactly what I'm talking about.)
From a gameplay perspective, I like the implicit or explicit choices inherent in a lot of games, but like all other choices I make, my immediate environment will affect the outcome. Alone, I can be the picture of mercy, choosing to spare the life of someone who really ought to die; or unabashedly evil, torching a perfectly innocent creature just for grins. In most multiplayer, any behavior outside the 'acceptable' curve is outright prohibited (damn team-kill protection), counter-productive (damn linear paths), or heavily frowned-upon (damn stat-conscious players). You can make the case that such restrictions are desirable, even necessary to maintain the flow of the game; and I would agree, in some cases. But this tends to overlap with a lot of inexcusable deficiencies I know I've previously complained about; let's settle for just naming a few of them, to wit: unnecessary assistance (aggressive auto-aim, 'hints' of all forms), unnecessary restriction (ye olde 'invisible walls'), unnecessary praise (achievements, one and all). You could certainly argue that single player games share these flaws, and indeed, even exacerbate them. But I am free to take them at my own pace (unless it's a mandatory tutorial sequence - man, _fuck_ those things).
One other point I'll bring up: mismatched skill sets. In any multiplayer game, you're guaranteed to have players develop unevenly. Some are just more inclined to tactics than others; or predicting enemy movements; or memorizing weapon stats; or executing impossible jumps; or recognizing obscure patterns - you get the idea. On an even baser level, some people are more driven or have more time to improve. This amplifies skill mismatches, since the competitors - or, even more visibly, teammates - diverge more quickly. Hello, 'Catch-22' - you can't improve without playing and facing a greater challenge, but you don't _want_ to play when you're getting absolutely destroyed. The critical point is so small and so easy to miss that many will not even try, and lacking a comparable offline or single-play mode certainly doesn't help matters.
Don't get me wrong, a good, fast-paced multiplayer game can be quite fun - case-in-point, our recent Winter-een-mas party was greatly enhanced by Nidhogg and Starwhal, two very enjoyable, (almost) entirely multiplayer titles; and Jamestown is a recurring favorite of the more 'twitchy' players (myself included). There's a lot to be said for the camaraderie and (half-)joking exchange of thinly-veiled insults and threats, and the joy of discovery inherent in bringing the occasionally completely unknown (to the participants) game to the table.
Still, there's also a lot to be said about the depth and range of experiences gained playing alone. In all my years as a gamer (a term I use unapologetically and unashamedly), the vast majority of my strongest memories of games have been from single player titles, or even practicing multiplayer alone: sudden bursts of laughter from absolutely absurd dialogue or odd character behavior; undying fury and / or frustration with difficult mechanics or poorly-implemented controls; absolute elation with both edging out or utterly destroying a previous high score; deeply embarrassing dancing and singing - were it actually witnessed by a third party - from simply completing a segment or the entire game; shedding tears (sometimes continuously or repeatedly) during many ending sequences. We humans are a curious lot - no matter what we may tell ourselves (or others), some can only be truly comfortable in their own company.
