I realise now this is a silly question, it's a spectrum from 10 minutes to 10 hours based on the genre you're playing and beyond even 10 hours. Many RPG's have tutorial based stuff going after 10 hours but you're likely going to know if the game is for you or not at it's core if you're familiar with the genre, shortening that time. I gave Dark Souls 2, 20 or 30 hours even though I somewhat enjoyed that. I've given Wrath of the Righteous 30 hours yet only gotten into the games campaign at 10 hours and again enjoyed my time so I'm actually in the camp of as long as it takes and I didn't even realise it until just now. I've given Racers dozens of hours to upon up and allow for certain sports I want to play the most lime Rally cross in Dirt games and most hardcore of all I spent one month, a month or five or six weeks of no lifing and rushing Final Fantasy 14 online to reach the first expansion (I was in a rut in life) where the game apparently got good and it did. I had bits of fun along the way but I certainly wouldn't say it was an excellent experience and really sluggish innparts, I thought about quitting a lot but people kept saying press on, only then did I start getting really addicted to the game in the MMORPG hard drug level addiction.
Man, I completely blocked all that out when I made this thread, the above makes 2 hours look like the blink of an eye.