There are some similar card games that you might find in a casino, but poker is pretty special in it's ability to work in a tournament format. Firstly it is quite a balanced game, in theory if all players played a perfectly logical mathematic game then bluffing and the psychology behind that is what creates the biggest skill difference. Secondly, it can stretch for a long time and is stretched even further when you start with many players (e.g. 9) per table and this can be expanded in a knock-out style setup across as many tables as you can offer. Then there are many auxiliary benefits, like a simple to understand format and an ability to control the tempo of the game with things like an ante level.