IGN seems to disagree with the length of your playtime -
10hrs vs 5hrs is a significant discrepancy. They also talk about large scale battles and bosses (also contradicting you here). Not trying to say you didn't play the game, but it seems like you either didn't get as far as you claim, or you just didn't like it.
I just went onto IGN and read their review before seeing your post and I was going to say the exact same thing. Now Im a little confused between what IGN said about the game and what the OP said. Guess Ill just have to read more reviews to find out...or probably just buy the game and find out for myself. Probably the latter.
Just about every review I could find praises the campaign, even more harsh and realistic ones like Eurogamer's. Most also say the campaign is a good 10-hrs, so I don't get him.
A good deal of the reviews surprised me, as in they are a lot higher than I expected. Then again, contrary to what some say in here (that Resistance isn't of high quality or of "similar quality to Ratchet & Clank"), the franchise has stapled itself as a key FPS franchise for it's supported brand. I was someone that really enjoyed Resistance 2 (although I was a tad disappointed with the removal of the weapon wheel). With that back and the thumbs up from gamers/reviewers alike, looks like I'm going to enjoy this! Have to wait till November 2nd though, I'm getting my copy with the PlayStation 3D Display.