Top 5 Best Slot Machines in Vegas. On average, slots at the Vegas strip have an RTP that ranges between 75% and 98%, which means that the player is bound to receive 75-98 cents as a probability return on a wager of $1. The best part is that the gambler does not need to be an expert or a big wig to spin the slots. 3. 1429 Uncharted Seas Slot - 98.60% RTP. Next in the line of high RTP slots is 1429 Uncharted Seas Slot, that has an RTP of amazing 98.60%. The slot is powered by Thunderkick software platform and features 25 paylines and 5 reels. Apart from the high RTP, the game comes with symbols such as ships, mermaids, the sun, the moon and the stars. Not surprisingly, the penny slots are the worst of all. No matter where you play them, the best average RTP in the reporting period was only 90.88%. The highest average, 96.41%, was found on quarter slots in off-Strip Las Vegas casinos. But overall, Boulder Strip casinos had the highest RTP average out of all categories.