Topolino's at the Riviera resort is fantastic. They do a character breakfast/brunch until ~1pm (the food is actually great -- which is not true of all character meals) and then a dinner service (no characters). It's on the top floor of the resort so views are incredible and the resort is fun to explore as well. Their quick service, Primo Piatto, is very good too for a lunch option.
A short walk from the EPCOT stop are Yachstman Steakhouse (Yacht Club) and Flying Fish (Boardwalk) -- both serve only dinner and are delicious. I'd give my slight preference to Flying Fish. Ale & Compass is also at the Yacht Club and does both lunch and dinner and is solid and a bit more moderately priced. There are also some good options over at the Swan and Dolphin - Il Mulino, bluezoo, Shula's. - a bit further of a walk but not by a lot (all of these are also dinner only).
If doing dinner, just pay attention to park closing times so you can gauge when the skyliner will stop running - if you need it to get back to Hollywood Studios or your resort.
We've done both Topolino's and Sebastian's. Sebastian's is definitely the better "bang for your buck," but requires a little more walking from the Skyliner station. Topolino's has VERY good quality food but obviously, a bit more expensive and a little harder to get a reservation.
I haven't done the Quick Service options (Spyglass Grill and Primo Piatto) at either resort but I heard they're both pretty good quality food.
I'd do anything in the Epcot resort area (Yacht Club, BW, Dolphin). I've eaten at Topolinos and while the food was fine, we didn't have great service and since it was December and they were having a cold snap, we couldn't go out and enjoy the view from the terrace. It didn't live up to the hype and price for us, but it was when it first opened up and we were a table of two (it's been my experience they give the two tops to a server that also has a big table, they tend to pay more attention to the big table, I'm assuming expecting a bigger tip).