In a word, everything.
In life you need to sleep, eat, drink, piss, shit, run the daily risk if getting sick or injured, worry about money, face society and law in manners that actually have consequences, wait in real time, there's no fast travel, no extra lives, no superpowers, no saves, no reset, no time travel, no mods, no console commands, no cheats and even if play by all the rules and play it with 100% effort it ultimately results in death no matter what.
Video games are great, and life sucks.