Hey man... i feel your pain. There are so many different cases, and all of them claim to be the best, and each cost anywhere from $10 to $30.
I hope you take my advice here, as i've honestly tried a bunch of cases. I've tried a handful myself, returning, exchanging, etc. at the apple store. Then my girlfriend has tried a bunch as well, and so have my friends.
I can tell you this much, go with an Incase brand, silicon case. They fit the tightest around the phone, give you a good grip on the phone in regards to holding it in your hand, and the sides won't be loose like your belkin and other silicon cases. Also, you can still use this one on a dock, as the bottom has a perfectly shaped slot for the dock. You can keep this in your pocket with no issues.
It looks exactly like this, and it fits SNUG! The case is a silicon rubber and will absorb impact if you drop the phone but is hard enough to be very tough.
They come in various colors.
I'd also go with an anti-glare screen protector. It makes the phone so much nicer to use. The screen protector will fit right perfectly to the screen, the case edges slightly over-lap the screen protector so there is no risk of it coming off or getting dust under it.
The anti-glare screen protector will make it so you NEVER get smudges, fingerprints, or anything on the screen. They are waaay easier to clean than the crystal screen protectors, and have absolutely no glare. The picture on the iphone is so much better with this on it than other screen protectors. It essentially takes away the shiny screen, and looks more like you are looking at an LCD screen without the glass front. Awesome. I tried having the phone without a screen protector, then tried using the crystal (shiny) screen protector, and hated it both ways because of the marks that were constantly on the screen. The anti-glare one removes this issue completely. No more marks, period... and dust wipes off easily.
Do yourself a favor, and buy both of the things I just listed at the apple store. Out of all the cases I bought, this one is by far the best. Oh, and the cases are different for iphone, and iphone 3g.... because the phone is shapped different. So, make sure you get the right one for your phone.
In case you were wondering, my girlfriend has an Agent 18 silicon case for her iphone 3g. She likes it, and it's a great case as well.