I see MPGe as a (the only?) way to compare similar vehicles to each other: BEV vs another BEV or PHEV vs another PHEV. It lets you compare which of them is potentially cheaper to run. It's not really meant to be used as a direct comparison between a BEV and an ICE, mostly because of the wildly different costs of electricity in the various parts of the country. That's not to say that gasoline prices are all that stable either.
To me, the only way to compare BEV vs ICE in electricity (MPGe) versus gas (MPG) costs is to figure out how many cents per mile each vehicle costs to operate in the environment the owner lives. Last year I created a simple spreadsheet to calculate the costs involved, using typical values/figures here in San Jose, CA. Assuming that an EV uses 300Wh/mi, electricity costs $0.38/kWh and assuming a charging efficiency of 95%, the cost comes out to $0.12/mi. An equivalent ICE that gets 40MPG with gasoline cost of $4.79/gal (remember I'm in CA and this was last summer) is the same $0.12/mi. If gas is half the price, then a vehicle can get 20MPG and still be $0.12/mi.
However, if the BEV owner has charging availability at their workplace (for free), then the cost to operate would be closer to $0.00/mi. You're not going to find that many places where companies are giving out free gas to their workers unless it's a situation where the employee is using their car for company business and they're getting reimbursed for mileage costs. But that would only cover the times when they're "on the clock". Costs to run errands to the store, take their kids to afterschool sports, go out for a Sunday drive, etc. should not be covered.
At the moment, my car (2018 LR RWD) is getting about an average of 280Wh/mi. I charge at a (subsidized) ChargePoint station where it's $0.19/kWh. That makes my cost $0.06/mi. Assuming that I was still driving my old 2000 BMW 323i (25MPG on a good day), gas would have to be $1.40/gal. Or said another way, with the cheapest regular gas currently running about $3.99 (gasbuddy.com using 95120 ZIP) near me, I'd have to have a vehicle that gets about 71MPG.
If I charged at home, PG&E costs are about double what I'm paying at the local ChargePoint station. That's why I've yet to install my Gen2 Wall Connector. Yes, it's a little bit of a hassle to go out for an hour once every couple of weeks to sit at the ChargePoint station but I'm retired, don't drive that much, and I try to combine the charging with other errands I need to run.