The more modern digital screen slot machines I've played now have 2 buttons, one that selects how many paylines, and one that selects how much money per payline you bet, and have rewards that can trigger minigames. I wouldn't say they're more engaging or fundamentally different than classic casino games, but I think for casinos there will always be an incentive to design games that can be optimally played by any drunk player.
On the flip side, as someone who used to be an obsessed video game player, behind all the fancy media assets, all I see in most videogames is running through a maze and watching the output from pseudorandom number generators.
To make a casino game that is actually fun, by gaming standards, I think it would look like World of Warcraft with an in-game integration of marketplace for gold and items instead of going to ebay.