if your looking for fun and enjoyed the original ruby/sapphire ORAS is a good game with great features.
if your looking to play competitive USUM is the way to go, the game itself is enjoyable to play through also.
I would personally recommend Ultra Sun and/or Ultra Moon for the following reasons.
1. Great year to have the newest games, Monthly Events (official nintendo releases)
2. The Games are fun
3. Great for any type of player
4. not hard to get from casual adventurer to ready for competition in this gen
5. Shiny Hunts, if your a collector or just like legit self earned shinnies
6. the alola region has much to offer
again that's just my recommendation based on my opinions.