1. Halo: CE had the best story of the three primary Halo games and those you mentioned in the first paragraph. I understand that it's an arguable point, but I'm speaking from a strictly structural point of view.

2. Campaigns in video games are getting shorter because the plots in the stories are more interesting and, as such, need to be more condensed to maintain pacing and flow.

3. Agreed, multiplayer does not define the game experience. You should understand, however, that the casual gamer is the largest demographic to play video games and the competitive gamer is the largest demographic to purchase games when they are first released. Highlighting good multiplayer is a marketing tool, as well as an extension of a game's primary function.

4. The cover system employed by Gears and ME2 was pioneered by an underappreciated game called KillSwitch, which was then revolutionized by Ubisoft for Rainbow Six: Vegas. Gears is by no means original and ME is not copying Gears. RS:V2 was far more successful than either of those games. Cliff Bleszinski said himself he took inspiration from RS and made the cover system more like a game of paintball, which multiplayer strongly represents: People hiding behind cover until some one hacks you to bits with a chainsaw

5. A game can't have everything. I don't think, and hundreds of thousands of other people will agree with me, that a game like Oblivion is incomplete or lacking in any way. MW2 certainly has multiplay failings, and the character in gears 2 doesn't move quickly enough in multiplayer for my tastes. There are plenty of single player games out there that are interesting and have multiplayer, like MW2, RS:V2, and Gears 2, that don't hurt the experience of the story. Halo: Reach and ODST are great examples. Just don't let the multiplayer bother you.

6. I never experienced turn-based strategy in DA, and I don't believe it was ever marketed as such.