Right next to the entrance to Rocky Mountain National Park sits the Trailhead Restaurant. It is in a string of buildings that includes the Fall River Visitor's Center (open seasonally - ie., not in winter), an expansive gift store, and the restaurant.
My experiences have been consistent with other reviewers. Some of the options are quite good (hot, fresh fries, the wraps, and so on) and others not so great (the elk stew, some of the burgers). I've never eaten breakfast here, so I can't comment on that but the breakfast menu looks good.
The service can be a bit slow, but other times it has been pretty quick. I think it depends on your server.
The scenery is awesome - looking towards the park and towering pines as you eat.
The adjoining gift store - which has 2 floors - has something for everyone. From the usual stuff (t-shirts, mugs, etc.) to the exotic (handmade wooden crafts, night lights, lotions).