4th was just a glorified video game in tabletop form. I didn't mind it other than it homogenized all the classes in a way. But using it for a video game would just be redundant. Video games already use tons of skills with cooldown or whatever.
5th is more clearly related to 3 or 3.5. But it replaces non stop plus or minus modifiers with debates with the GM. Things don't get +5 or -3 or whatever, instead if a roll is advantaged then you just roll two die and take the higher roll, it's the opposite with disadvantage. And anything can be given that effect depending on the situation. It works fine, if very simple, but it's better suited for actual role playing with people. A computer can easily handle the math behind the scenes so why bother with it.
I hope the new BG uses 3.5 since u feel that engine is better than 2nd but either works better than 4 or 5.