Video Poker is a great choice if your going to play slot machines -- it's one of the few games that you can actually influence the odds in your favor by playing correctly.
That said, there are some video poker machines that pay out better than others and you can tell by looking at the payout table that is posted on every machine. If it's not posted (which is the case on machines that offer multiple versions of video poker on one machine) there is always a screen available on the machine to see the pay table for that game.
In a typical game of Jacks-or-Better Video Poker, what you want to see and pick is the classic 3-6-9 pay out table. It is called this because with a one-credit play you will win 3 for 3-of-a-kind, 6 for a flush, and 9 for a full house. These also typically pay 2 credits for two pair. This is the ideal pay table and pays back an optimal player at 99.5%.