An electric car that gets driven at least 70-90k miles is more sustainable than a gas car, but that's like saying that being hit in the kneecap with a ball peen hammer is better than with a sledge hammer. It's true, but we're still not having a good time! For EM's (electric motorcycles), that number is probably lower because motorcycle fuel efficiency is not tremendously higher than a gas car and EM battery sizes are 3-4x lower than electric cars. However, the majority of American EM's are probably not ridden enough miles to hit the break-even point compared to gas motorcycles.
The rub is that you have to drive the vehicle a lot to hit the break-even point, but high VMT (vehicle miles traveled) is inherently unsustainable, especially in a car. Even an electric car has emissions associated with it from generation and transmission of the electricity, it puts brake dust in the air, tears up the roads, carries the potential for crashes, and creates pressure against restoring our cities' land use patterns to focus on human beings and not motor vehicles. EV owners are less likely than gas car owners to complete a trip by walking, riding a bike, or using public transportation because they feel that they are already doing their part for sustainability by owning and using an EV.
I am not aware of any similar studies for EM's (research on them is very scarce), but the impacts of EM trips should be massively smaller, especially considering the lack of noise pollution in populated areas compared to gas bikes.
All in all, the picture is complicated and shows that EVs are not a slam-dunk for sustainability as they've been portrayed. I'm not anti-EV, but I no longer believe that everyone just needs to drive electric cars and everything will be fine, and I definitely do not believe that we should still be subsidizing the purchase price of expensive vehicles that are largely bought by people who work from home and will likely never be driven enough miles to break even with a gas vehicle. Just like the oil and gas industry 100 years ago, subsidies that were designed to support a nascent industry are now fueling the profits of an industry that is already powerful and politically connected.
I understand this is probably not a popular opinion around here, but there's my 0.02.