Maybe you had the wrong new rechargeable AA's. The Eneloops (and other low self discharge rate batteries) are great and well worth the small premium they cost.

Now, that said ... a single NiMH AA battery contains about 2.4 WHr of power, and an 18650 battery about 9.0 WHr. The 18650 is a good deal larger, and Liion and LiPo are known to have higher power densities than NiMH, so this shouldn't suprise anybody that a 18650 can provide more energy -- though 4 AAs would give it a run for its money.) But when it comes to the discharge rates when the batteries aren't being used ... both the Eneloops and the LiPo/Liion (I'm not sure which) 18650s are excellent, and both will have over 80% of their charge even after several months of not being used.

That said, 18650s are damned convenient, inexpensive and perform well. The single 18650 cell flashlights make great bike lights -- put two on your bars (using one most of the time), keep two batteries in your bag as backups and you're ready for pretty much anything short of riding all night (and you'd even be ready for that if you avoided the high light modes.)