When commuting you need to consider not only MPG but incremental and major maintenance costs as well. Things like insurance costs, oil changes, valve checks and tires will add up quickly and must all be considered. I used to commute on an '08 Versys. It was great, about 50 MPG, decent luggage options, decent running costs, etc. I rode it for about 25,000 miles in just under 2 years before moving on.
I now commute on a KLR, while not as good as the Versys in the power and spirted sense, it is better as a commuter in many many ways:
Tires are dirt cheap to buy and change (got spoons) and last forever!
Oil changes and filters are cheap
Valve checks are infrequent and take less than an hour to do.
Low tech means less to break or deal with
Longer range than a Versys and many other bikes
Insurance is stupid cheap for full cover, buy a cheap one and full cover is optional.
Aftermarket new and used is HUGE, making finding things like luggage and suspension bits cheap and easy
Expect about 50 MPG on a stock bike
Overall TOC for a KLR is pretty darn cheap, the up front cost is cheap and you can find a used one, fully commuter farkled out far cheaper than many other bikes. If it falls over, little to break and tons of aftermarket protection available. It is also less likely to be stolen than a lot of other bikes...and finally, you can ride it almost anywhere at any time.
Certainly the Strom and Versys are better bikes, but for a commuter when cost per mile is a consideration, and you consider ALL costs, such as upfront, running and maintenance costs, you would be hard pressed to beat a used KLR.
As for small thumpers, I tried to commute on my KLX250s with some Wolfman luggage, it was okay, but in the cold I wanted more wind protection and a bit more amps for heated gear, the KLR fit perfectly.
2007 BMW R1200RT
2002 Honda XR400r