For a nice lunch at Vail, go to Sweet Basil in the Village. It's often quieter at lunch than dinner, when you have to make a reservation weeks in advance. If you want good deli, then Joe's Famous Deli in the basement on Bridge Street. I think Larkspur, which is the fine dining at Golden Peak, also serves lunch, and it is an upscale atmosphere.
Keep in mind that Vail is HUGE, though, so if you go to the bottom for lunch, you're not going all the way back up! You might consider late lunches there, and calling it a day. I actually enjoy do enjoy eating at Two Elk on mountain, as it is beautiful (although get there early--11:15ish--if you want a good seat). And I like Belle's Camp, at Blue Sky Basin, where you can bring your own meat and grill it on gas grills while looking out at the Holy Cross Wilderness.
At Keystone, I would suggest eating on mountain, at the Alpenglow Stube. Make a reservation! It's at the top of the gondolas, and when you walk in they take away your ski boots and layers and provide you with (heated) slippers for the duration of lunch. There is an extensive Bavarian buffet with cold meats and smoked fish and salads and cheeses, then a table-served entree, and then another extensive dessert buffet. Good wine list, nice experience eating in relative luxury in your ski clothes with your heated slipper and snow and mountains outside the window.