I had my first Five Guys experience a few weeks ago at the urging of some co-workers - "It's the best burger ever" blah blah blah. I had the same as you -small burger and split a fries. I found the food thoroughly average. At 12:30 on a Friday, the place was near empty.
I couldn't help thinking 5G may suffer the same fate as Krispy Kreme did in Canada - lots of hoopla, rapid expansion, bankruptcy, rapid contraction.