There are several lights below Alien Bees if using a rating scale. Mostly available from e-bay dealers, but a few are on BH. ABs are actually somewhere in the middle of the scale.
I would personally vote for Elinchrom at the top, without considering commercial studio grade options.
For example while I would have rated my Dad's Norman's at the top of the scale at one point, these days my ABs are better lights overall with a lot more control.
I think that someone with too much time on their hands could probably do a comparison using the following factors (the first 3 are primary, the rest are secondary):
1. Wattsecond rating (both real and effective
2. Range in F-stops available
3. Cost
4. weight
5. Monoblock or Pack/head (I would give a 1.1 to 1 ratio for monoblock over pack/head, but this might be subjective preference so maybe not include this in rating value)
6. construction (durability)
7. versatility for travel
8. white balance (both color and consistency between shots)
9. Other features
10. User feedback
11. Availability and ease of replacement/repairs
12. Professional look
13. Control mechanisms (such as PW compatability or ABs RR1 system)
14. Light modifier commonality
I am sure I am missing a few. The tricky part would be to assign values and basis for values and then factor in user reviews.