In my experience, different things work at different times. We have a battery of products that we used for diaper rash:
1. Bag Balm - stinky, but good
2. Burt's Bees diaper cream, has zinc oxide - this was our standard cream most of the time
3. Palmer's Diaper Cream - smells like chocolate
4. Homemade mixture for really severe rash: 1 part Bag Balm, 1 part zinc oxide, 1 part yeast infection cream (Monistat, Vagisil, etc). I normally don't like pulling out the big guns, but it really helped one month where my son had horrible rashes.
By far, the best cure for diaper rash we've found is naked time. Letting my son air out his butt overnight (sleeping on a waterproof sheet) and leaving him unclothed at home in the evening/on weekends really does the trick. The more natural light exposure, the better!
Best of all, my son just recently started using the toilet on his own (at 3) and now he has no more diaper rash! Yaaay! In fact, he started toileting right after getting an awful diaper rash. He hadn't had one in a long time and this one was a doozy. I told him, "If you would poop and pee on the potty you would never get diaper rash again," and that was it!
Good luck!
Edited to add: One of the other posters reminded me of something! I agree, don't use diaper wipes! Even the "mild" ones have chemicals and stuff in them that your child could be sensitive to. For daycare we would send those kind of commercial wipes, but at home we use flannel wipes and plain water. They work great and are very cost effective. Have you considered cloth diapering? It's a little bit of a hassle when you first start, but once you get the hang of it it's easy peasy and helps a lot toward preventing diaper rash (again, in my experience).
Good luck again! :D