If it is a developer that I've never played a game of theirs, I'll buy used. It won't be $60 then. More like $20.
If I liked the game, I'll consider purchasing their other content at $60 but it will still depend.
I like quality. I also like a good quantity. I've become used to 8 hours but on a first run, that is a bit short. I will admit that it is difficult to develop a good story line and not make it feel like it is dragging out.
There are games out there that do deliver both but some of their "filler" content is finding stuff...GTA series for example and all their egg hunting of various types. The main stories seem to be 8 hours though. GTA III I bought used, the rest I purchased new.
If I can replay the game several times without doing it the same way as the previous times, that is a good thing in my book and I don't mind paying new price. Resistance and Duke Nukem for examples. Lots of fun weapons to play with and I didn't use some of them the first time through so I played again using all the other weapons I didn't use. Borrowed the first Resistance from a friend, bought the rest. Duke Nukem, well that I was intrigued the first time and bought new and will buy all new because those are just well done games. In Duke Nukem's case, it is the little stuff that makes the game interesting because it is funny. The first run through is about 8 hours but since I will enjoy replaying this a few more times, I don't mind so much.
Normal/Hard/Elite is OK if there is some variation. It seems that most games just make the critters harder to kill and better shots though. I like a challenge but it doesn't make them think any better but it is hard to program an AI.
It does seem though, most FPS are not really much different that another. A hero goes in with guns blazing and kills everything. Some games such as the first few Ghost Recons were different because you could place a team in a spot and they would typically cover that spot. I didn't like where the game development went after the 4th one because they got rid of what I really liked but I replayed the first three several times because it was well developed in game play. The first one I purchased used, the others I bought new.
Never got into SOCOM because trying to learn the mechanics on the first game, the AI was so completely stupid that my team member would be getting shot at and still try to freaking sneak. I haven't bought any of their stuff since. It is a good concept and it seems to be geared to having real people but I won't buy any other SOCOM title because of that first game. I heard that is was a great game from people I knew so I bought the first one new. I regretted it.