Metroid Prime 3: Corruption misses out on online play

Well, I don't see how it wouldn't. They'd have to either throw a bunch of people at it, which would mean less people working on the singleplayer - or throw a bunch of money at it to hire outside help for the Multiplayer, which would tighten the budget for the project overall (Obviously affecting the singleplayer). Unless a third party stepped in and threw money at them saying 'Here, you can use this to add Multiplayer to MP3' and Retro took it then said 'Nah, we don't want that but thanks for the phat cash'... but I doubt that happened

I don't think that Halo 3 is the best comparison to use, largely because with Halo the multiplayer has always been (arguably) equally as important as the singpleplayer - if not moreso. With Prime that doesn't really hold true, even though there is a small argument there due to the multi mode in MP2, but given the generaly concensus of 'What the hell is this here for?' I'd say thats more of an argument against it than anything else. Also, given the success of the Multi oriented spinoff 'Hunters' it'd make more sense to keep that as its on separate entity and build of it instead of trying to emulate it in Prime 3.

Basically it comes down to how important it is for the series I think. MS will be willing to give Bungie lots of assistance (if needed) to ensure that Halo 3 has the single and (especially) Multiplayer oompf to sell their console and continue selling Live! subscriptions. Nintendo just don't seem committed to the online space, so I don't think they'd bother trying to twist Retro's arm on the matter.

I'd argue that nowhere near every single game attempts to have a convincing singleplayer element, but that'd just be needless semantics.

I think that multiplayer doesn't suit Metroid Prime, unless they were to tie Prime 3 in with Hunters. As I said before, it would make more sense (to me, anyway) to keep Prime as a single player story driven experience, and continue the Hunters franchise separately for Multiplayer Samus (and co.) action. To me Cer's example of multiplayer in Zelda is perfect - people only seem to expect a multiplayer mode in Prime because it's a first person game. No matter how you want to argue it, and no matter how many definitions are cited, the Prime series just isn't a 'first person shooter' in the traditional sense and really doesn't need a deathmatch mode tacked on to it just to placate the masses who think that any game with guns in it isn't complete without multiplayer.