Those are some of the worst battery stats I have seen. I go all day talking about an hour to two hours a day on the phone. Depending on talk time I will be down to 50% or 25% somewhere in there. My GF is using my old 2G and it actually has a slight battery life decrease than the 3G but not bad (drains maybe 5% faster). We have been using that one for over a year and it lasts the day as well. In the ocassion that I don't use the phone I have let it sit for 3 days and been at 30% (have only done this once). Unless you have bundles of apps draining your battery I would say its a harware issue. Give the Apple store a visit
It does kinda suck that apple doesn't do removable batteries doesn't it? I mean what an inexpensive hassle free fix this could be (assuming it is just the battery at fault)