It's true that package managers solve the distribution issue, and a great way
to achieve what BrighamKeys is suggesting would be a libre games PPA, which
could be added to any apt-based distro.
However, I think the appeal of Steam is broader than just the distribution
mechanism. It's a graphics-rich, content-rich portal that facilitates
discovery of new games to play. There are also social features (that some
would consider "gimmicks") like achievement tracking, and hosted forums for
all the games. Not to mention "Steam chat", which I believe is just XMPP, but
it's nice to have it integrated and automatic.
Then, of course, there's the elephant in the room, which is that Steam is
also a payment mechanism that allows the purchase of proprietary games. I
don't want to get into a FOSS-vs-prop. discussion here, but FOSS games don't
really have to solve this issue, as you can't really sell a download of a
piece of FOSS. (Well, you can, but there would be no incentive for anyone to
pay it when current holders are free to pass the software on for gratis).
Maybe we could look at something involving bitcoins here, but IMO that would
be for donations only, not purchases per-se.
