Eneloops are rated at a minimum of 1900 MAH. Some of their lines are rated higher (min 2200 MAH I believe), but the trade off is that they self discharge a bit faster and do not give as many cycles. Self discharge is not an issue if you just top them off before use, or use them within a week or so of charging them.
Most alkaline batteries are around 2500 MAH. But the voltage on alkaline cells drops faster with charge level and will nosedive under high current drain. . Meaning that they also are pretty bad for anything that draws much current.
Often the NiMH batteries actually last longer in any given application.
BTW, there are many brands of NiMH cells, often cheaper, but fully serviceable. Many manufacturers of alkaline batteries also have a line of NiMH cells as well. It seems that most of the test/review sites rate the Eneloops at the top of their lists.
"Battery capacity ratings are meaningless when used to compare different types of batteries or to compare the capacity of batteries powering different types of devices.
This means that you may not be able to predict how long your electronic device will run just by looking at the capacity rating of a battery. For example AA alkaline batteries typically have a capacity rating of over 2,500 mAh and AA NiMH batteries have rated capacities of only 1,200 to 1,900 mAh. But when it comes to actually powering an electronic device like a digital camera, the NiMH batteries will often run the device for three or four times as long.
(for an explanation see Battery FAQ, Why do my alkaline batteries run out so fast?)"