Yeah you have 90 hours of TF2, and a million hours of WoW, and the keyword here is "you". I have over 200 of TF2 in-game, and god knows how many in hammer. On the other hand I have played Portal through so many times now that, I'm not kidding, I must have clocked over 20 - 40 hours on that game by now. I have hundreds, possibly thousands of hours in GTA Vice City for the PS2 and even seemingly "low single-player longevity" games, like the Tekken series (again, in single player), have seen me net hundreds of gameplay hours. Meanwhile, and while I did have my MMO "phase", I never clocked nearly as many hours on any of them. In an argument like this, where the question is "is the subscription based plan better - FOR THE COSTUMER" you have to null out parasitic variables which otherwise influence the result, specifically, enjoyment of the game itself. In order for this "study" to be accurate, you have to assume people have the capacity to enjoy a P2P MMOG much in the same manner as they're capable of enjoying any other retail game... And if Steam profiles are anything is solid evidence that such people do exist.
And when you come down to it, is "renting" better than purchasing? Then for the most part the answer is no. Specially considering most of these "subscription based" services also force you to buy the actual game. That's why we usually buy our games, we don't rent them unless we're not planning on dedicating more than a bored weekend to them. The longer you have the game, and the longer you play it, the worse deal renting becomes. As said before, the added overtime cost of a "renting" anything forever (to equate ownership) is nothing short of infinite, which is slightly more than 60 bucks. Then there's the whole issue surrounding the fact that you never actually own the game, merely a temporary license to play it.
What you discuss in your article, in my opinion, deserved another approach entirely: Are P2P MMOS "that bad"? Cause that's a whole different deal. MMOs in general run on company-based servers, the cost of which is supported by the company, which in turn requires a steady source of income to support the servers the game runs on. A P2P plan in this case seems sensible (even though undoubtedly a lot of those 15$ a month per person goes into lining the company's pockets more than running the servers) and, some would argue, a better approach for the MMO world's "ambiance" than the "Free with premium store" one. If you really do want an MMO, then your choices are pretty limited as "retail-only" plans don't cover server costs and thus aren't efficient for the publisher, and given the options, "P2P" is not that bad a choice.
As for "length" of a game. Again, it's a slippery slope isn't it? First of all because longevity isn't everything. The time-proven slogan "quality>quantity" rings truer than ever here, and good single player games are generally built more towards a strong impact/experience than a longer lasting but more diluted one (i.e: mmos). But again, that's not the point of the article, so we need to assume there are equally enjoyable on both sides... That said, we stumble upon two more fallacies in your logic... First, that all p2p MMOs have good longevity while only SOME retail games do, which is a pretty big gaping hole in your theory. You use WoW as a comparison, but WoW is arguably the biggest behemoth of the subscription based MMO world, if not of all the MMOs, long held as the "king" of "MMORPG-land" every other MMOG attempts to dethrone... It feels tragically quaint to then pitch it against "average" games. Pitch it against equal "retail" behemoths like TF2 and CoD4 and suddenly the "gameplay time" field looks considerably leveled. If you wanna pitch it against "lower games" then you gotta pick a "lower class" of subscription based MMO as well. Perhaps one of those "WoW killers!" that surface every other month and go down under after a year or two (deja vu of "Halo killer!"s?). The other gaping fallacious hole in your theory revolves around your usage of hours played to correlate with price for the estimated price "per minute played"... This is pointless because you don't pay for your minutes, you pay for the hole month. 4 hours of WoW can cost me the same as a full "retail" game, I just need to play 1 hour a month. Ultimately you need to clock how many different months have you played these games? Even if you turn the game on once, log in your character, walk around, log off. That's one month you'd have to pay in subscription based services.
Anyways, this is becoming a rant, my apologies. I think I got the point across: I think you let your personal bias get the better of you in this one.
