Look, a route between any cities under about 500 miles apart is a candidate for a high speed rail route. That isn't to say all such routes should be built, depending on cost, difficulties of assembling rights of way, populations in the cities and expected ridership, etc.., but for such distances such routes are easily competitive with air travel in terms of customer preference.
The limited stop train makes it from Barcelona to Madrid, about 385 miles, in 2:35. That's city center to city center, no need to travel to/from the airports, no need to show up to the station an hour and a half beforehand, etc.
