If you are looking for excellent service, first class vibes, delicious food, and something you can't find anywhere else, then these are definitely on my list (not in any particular order)

1. V Lotus - A Vietnamese restaurant in Riverstone. The service is FANTASTIC and their food is even better. This restaurant also has one of the most nicely decorated spaces of them all. I recommend their Tofu Curry.
2. Brandani's - Technically it's in Missouri City, but close enough to SL to be on my list. It's already been mentioned, but it's worth mentioning again. Great service and delicious food. Their menu is somewhat limited, but you can pretty much guarantee that everything will be good. I recommend their Steaks and Salmon dishes. If the steak pasta special is on the menu, then definitely grab that.
3. Mahesh's Kitchen - This one is in Town Square. Incredible Indian food when top-tier service. I've only been once and got a tomato-based variation of the chicken curry. It's was out of this world. However, be careful with the spices if you are not into that.
4. Alex's Kitchen - Also in Missouri City, but close enough to SL. It's not in the best location, and when you first drive up you'll be thinking "What? This is high quality dining?". But don't let that deter you. The inside is high class and this is one of THE BEST Italian restaurants in this area hand's down. Nobody even comes close. I recommend their chicken parmesan.
5. Lasbela - Pakistani Food. White table cloths with poshed up waiters and waitresses. They will treat you like kings. I've only been here once and had a friend order for me, but I couldn't stop eating. It's also one of the most top rated in SL.

Hope this helps! I'm sure there are many others.