Actually bruschetta is fundamentally toasted casareccio bread (large-holed, rough big artisan type bread), with garlic rubbed on it and olive oil, salt and sometimes pepper.
Anything else added is an extra, but i;ve never (ever) seen them with cheese.
tomatoes are common, but if you just ask for bruschetta in Rome, at least, you get just bread, garlic and oil. If you want tomato you ask for it, or in rome they sometimes call it panzanella, though that is used elsewhere to refer to a bread-based salad, with tomatoes, cucumbers, etc.
Crostini depend on the region. In Roman pizzerie they;re usually slices of baguette type bread, lined up or overlapping, with something like prosciutto and mozzarella, or anchovy and mozzarella on top, then it;s put in the pizza oven to toast and melt the cheese.
In tuscany it;s like canapes usually involving liver and vinegar spread on them, but i think can be made different ways.
For bruschetta (broos-keht-tah) think rough kind of thing, simple peasant food, for crostini think something more refined, maybe.
Then, of course, there can be more regional variations i don;t know about. But cheese on bruschetta - never saw or heard of it. (Not that you can't do it, there are no bruschetta police, but if you want to know what the words refer to in italian, there is no cheese)