Video poker

Video poker is the only machine game where you can calculate the return before you play. The deck is 52 cards, the deal is random, the pay table is printed on the screen, and the whole game is solvable: 2,598,960 possible deals, 32 ways to hold or discard each, one mathematically best play per hand.

Which means the return is not a mystery to be estimated from reviews. It is a property of the pay table in front of you, and two machines side by side with identical graphics can differ by 2.2% because one pays 9 and 6 for full house and flush while the other pays 8 and 5.

The skill in video poker is entirely in two places: reading the pay table before you sit down, and playing each hand correctly afterwards. The first matters more.