Without proper info and data we are swimming in opinions and anecdotes and not able to vote for something rational.
Tax exemptions for aviation is a problem. A bigger problem yet is that the environmental costs are not charged to the user (in both aviation or trains).
But even considering that, I suspect the train tickets would still be to expensive, relative to aviation. And that is, in my opinion, due to the inherent lack of competition in trains and relatively easy to implement competition in aviation. Train and train infrastructure companies need more accountability --- big vehicles in dedicated tracks should result in very inexpensive tickets, why aren't they?