Quoting Snarkasm
Really? It's quite possible that both of them can be considered beta versions of their new final products - L4D2 and 7. Better AI, more content, some new looks... sort of like better performance, more functionality, some new looks...

Snark, do you have an answer for everything
Lets take the whole OS vs. Game argument offline for a second. It will get us nowhere fast, two different animals. Nothing changes that Vista sucked, the L4D does not.
Now, look at the history of game sequels. How many are new level packs for a popular idea? Mega man 1-6, Sonic the Hedgehog 1-3, All the 3D Zelda's change a few things up, but they are variations of the same theme, hell, ID had Quake I and II, then release III as a more realized, polished, and complete multilayer experience that some may have argued should have been an expansion to II. The Metal Gear Solid series feels like a continued variation on the same exact game play. Madden each year. Games based on Pro Wraslin, oh, this years will have more realistic cage physics!! Halo 1-3, 1 innovated console shooters, 2 added online, 3 was just more of the goodness from the prior 2, should Bungie give it away and say, hey, 3 was the game 2 should have been? GTA 3, Vice City, San Andreas, how many ways can you crash and car and murder a Hooker, are we saying RockStar did not have the right to milk an existing franchise? And the mother of all sequel making franchises, Street Fighter!! You have the World Warriors, Turbo, New Challengers, Alpha, Alpha II, Alpha III (my personal fav), III, III thrid strike, I could go on all day on the number of sequels and variations produced, oh, and Capcom vs. Marvel, and 2, all basicly updates on a popular existing idea. Guess what, sequels fuel the game industry, if something is popular, if it sells, you milk the content until people grow tired of it, or in the case of Sega, do something retarded and try to make Sonic work in 3D.
Point being, in games, sequels that add a slight thin coat of paint to an existing idea are as common as opinions on the Icrontic forum. Are we suggesting that Valve does not deserve a slice of the Pie that so many developers milk over and over again? Why not call EA out for nabbing $59.99 yearly for a Roster update (I'm sorry, no amount of fancy marketing in the world can convince me that Tiberon is doing anything truly innovative). Lets ask Capcom to give each one of us that spent on numerous Street Fighter and Mega Man games a freebie because we got it coming. But Valve?? Don't gamers have bigger fish to fry?