And by that I mean not in a good way, negatively. I've been mostly playing 360 games for a while and I picked up a DS again recently. I've been having a lot of fun with FFTA2, Dragonquest IX, Mario and Luigi, Advance Wars, etc. So after I just finished Halo: Reach for some reason I was tempted to go buy a copy of Halo 2 and play through that a bit again. I was at the point in the game where you're supposed to snipe enemies off of a walking scarab and then jump onto it to take it out. Instead I'd been in a ghost most of the game to this point and I drove the ghost onto the scarab and beat the level that way.
That's when it occurred to me. This has been building for a while, be it my experience with the DS or the enjoyment I got playing PS3 games where trophies are fairly innocuous. Achievements were robbing some of the joy of video games from me. I realized that when I play a game that has no achievements I completely focus on the game. I lose myself in the game. For some reason when I play a game with achievements I check them to see what cool things I "should" do "immersively". The irony in that thought is rich, I know. I started to wonder why this was and this is what I think.
I think that 2 things may be happening. And this is just my theory, so feel free to squash it.
#1 - Games without achievements don't focus on designing mini-challenges as much. So something as silly as parking tanks in Vice City or finding ways to break a leveling system in a Strat/RPG to make a powerful character or landing a ghost on a scarab, these things all happen out of the mind of the gamer. It's your own personal experience. I may walk up to you and ask you if you did the same thing. May not of and you may not even know what I'm talking about. Your game experience is different. Your approach to playing the game might differ. Look at all the creativity people put into forming their parties in RPGs and how this varies wildly from person to person dependent on the amount of rope that gives them.
I think that with achievements, however, the game might be designed differently to make sure and create these opportunities to do something unique or unusual. I'm not talking about achievements like finishing chapter IV in a Halo game. I'm talking about a basketball game that encourages you to put down a certain statline. I might want to get a triple-double organically, but now that the game encourages me to do it, then it's not my idea. And if I accomplish it the shared experience will be how we did it, not how much our game experiences vary.
#2 - I believe that my own personal mindset changes. Without achievements I settle into just playing the game. I don't pay attention to collectibles. In Crackdown I didn't hit up FAQs to find all the orbs. I organically found what I wanted. I did, however, try to drive truck up a building. I did try to climb the agency tower. These are things I would have probably done anyway, though, so I enjoy them less and I find myself "coloring outside the lines" less frequently. When that achievement bell chimes and the icon pops up I instinctively go to check what I just did. Whereas before I might try random stuff out, like driving a ghost everywhere I can just because.
I'm sure I didn't do the topic justice. It's late and I am just stream of consciousness. I just now that I had MUCH more fun just now playing the much derided Halo 2 in part because I was achievement-free. Whatever cool and interesting things I tried to do in the course of the game happened out of an organic interest to push on the boundaries, not because the game told me what I may want to try.