It is falsifiable though. All you'd need is for someone to notice that a game that has been lingering in obscurity for years is actually great and start bringing attention to it.

There many games that only achieved success years after release (for example Psychonauts). It's the same thing as with films (my favourite: Blade Runner).

This is logical nitpicking and I don't even think you're right. It just implies that of all the games I've seen no great one failed. A game can be great by an arbitrary measure and still fail comercially.

Nonsense; the statement is true if he has seen exactly two games, both of which were "crap" and both of which failed.

The statement is also true if he hasn't seen any games. It's just an anecdote about his experience, that's fine.