Does a "factory/hard reset" actually work?

Not trying to be a pest but I'm wondering how I save things like saved game progress. Can I just copy the files over in the game folder back after the hard reset? Or are they stored somewhere else (like Windows 7)?
 
Did the hard reset last night and there's definitely a big difference. Battery life is back to what it was when I had 2.1. It's MUCH smoother, my internal memory has skyrocketed, Flash hasn't crashed yet once. The Sense widgets I have, Friendstream, People and Bookmark still randomly have to reload but w/e. Overall I'm very happy I did the hard reset. The biggest disappointment though is the video playback for 720P videos is still choppy as all hell. that's the only thing that really really bothers me. But overall VERY happy I did this. I did lose some contacts though. O well... Thanks everyone for all the help!
 
I was having alot of issues with my phone today so i decided to do a reset and BAM!! my phone is back to like it was before. I just moved everything to my SD card and removed it before i did the reset. I was on the verge of throwing the phone agaisnt the wall lol.