I just wanted to throw in my worthless, newbie to this forum, two cents... I think the problem with SP games nowadays is the lack of creativity being put forward. Its all about "how pretty everything looks" now rather than how good the story and characters are. Too much money put into the art instead of the writing.
Also... because I kept seeing people comment on how "good" the single player CoD4 is. I rarely play much MP nowadays and i LOVE shooters -- but holy hell, I could barely finish CoD4 because it was so incredible linear and insanely boring. There was absolutely NO story present -- it was all "ok now you are THIS soldier... and you are in THIS country... fighting THIS badguy!!"... repeat, repeat, repeat... game over. The single most overrated game I have played in YEARS.