they have a poor architecture for gaming? other than minor resources being used up by the OS and generally 1-2% of cpu power being used in the background for other programs, that ultimately makes no difference.
the gfx cards in consoles are the same(or close enough) to the versions we have at home. the cpu's, well some have been the same, P3 basically in the first xbox. yes they have fancy names but they aren't more powerful or better than PC cpu's. they just use different instruction sets but they basically work the same, program asks cpu to calculate if the bullet with set vector will hit anything, however it asks, or calculates, its still doing the same thing.
consoles aren't better value for money IMHO. you pay more for games, the console itself is subsidised so you get more for that actual money than you would buying computer parts. but everyone, and i mean everyone i know has a computer, every house, most kids/friends have their own computers aswell. the only thing you need to add to any box you build or buy is a decent gfx card. a 8800gts 320mb is a LOT more powerful than the xbox 360/ps3 gfx cards, so add a £175 card to a computer you already have and you have something much much more versatile, cheaper, and twice as powerful as a console, then games are cheaper.
i have had consoles, not many, not played them much and don't enjoy them much. basic sports "pick up and play" games i don't mind playing round a m8's once in a while, but they aren't games i can play a lot, console gaming has no lasting value for me and the hardware is often outdated before they are released(ps3) or within a few months like the xbox360. i wouldn't buy a 8800gtx the day before the G100 comes out, or the day after either.
i prefer multiplayer games where i don't lose half/ or 3/4's of the screen, i prefer to play in the comfort of my room in a nice chair without being interupted. the only real reason i see for a console is as a social gaming machine, and thats the only place i think they excel.