The Volt is still in a class by itself, it's the only true extended range electric car available. The Prius Prime is just a hybrid, 25 miles of electric range gets you to the grocery store and back and no more, that's just a tease. The i3Rex is just a short range electric with a limp home feature, it's not a road car. BMW's decision to put in a 2 gallon tank instead of a 9 gallon tank like the Volt's was a finger in the eye to drivers, it was done solely to please California regulators. I've done numerous 3-400 mile trips in my Volt and even on the longest I've gotten home with a couple of gallons left in the tank, you could never do that in an i3REX without stopping at every exit to fill up.
That said I really hope that the 2019 Volt at least doubles it's electric range and ups the charger to 7.2KW instead of the current 3.6. Although the 53 mile EV range is much better than any other PHEV available today it's really not adequate. A range of > 100 miles would make it a true EV for local driving purposes and the increase in the charger capacity to full Level II rates would make destination charging much more useful. For example we went to Portsmouth NH yesterday for several hours. There was free destination charging there but it was only able to add 35 miles (on the guess-o-meter) during the three hours we were there. I ended up driving on the ICE for a total of 50 miles during the round trip, a hundred mile battery range and full level II charging would have allowed me to do the entire trip on battery. Note that there are no BEVs available that could handle all of my driving, not even a Tesla. I wouldn't have dared do my short trip to Portsmouth in a Leaf because there is no way of knowing if the destination chargers would be available when I arrived, with the Volt I don't need a guarantee, if they are available that's great and if not so what. The Bolt could have made that trip easily but I couldn't go to Portland ME without a guarantee of a charger at my destination and I couldn't do any of my Vermont trips because there are no CCS chargers and no destination chargers at any of the places I go. Even a Tesla, which has the only fast charging network available. couldn't go everywhere I regularly go. Vermont would be doable because even though they only have 3 supercharger stations there they are all in the right places, it's not as good as the Volt which can do those trips with no stops at gas stations, but it's not unreasonable. I couldn't do my Maine trips, except to Portland because there is a Supercharger in Seabrook NH where you could top off if you needed to, because they only have two superchargers in the state and they are in the wrong places, there is no coverage on a seacoast route. For the next few years the Volt is the only fully practical electric car but I wish it were better.