Of the restaurants you've mentioned, Picasso and L'Atelier stand head and shoulders above the rest. I like Daniel Boulud a lot, and Bouchon is my favorite restaurant for breakfast, but they're not as good as the first two. I thought Wing Lei was interesting, and good, but not as good as the others.
If food quality is the only criteria, I prefer L'Atelier by a small margin. However, it's very informal. Picasso has a view of Bellagio's lake, great art, massive floral displays, and all around great atmosphere - all things that L'Atelier doesn't have.
Another contender should be Alex. I thought it had better food than any of the restuarants on your list, along with excellent service and atmosphere. It doesn't have the grand view that Picasso offers, but it's still very nice. Prices are a bit higher than Picasso, but in the same general range.
Lastly, there are a couple of super expensive restaurants, costing around $400 - $500 per person (including a modest glass or two of wine, tax, and tip). In addition to the crazy prices, a meal should take at least 3 hours, maybe more - so they're probably not good candidates for after the theater. Joel Robuchon at The Mansion is L'Atelier's big brother, and completely blew me away - food, presentation, service, and atmosphere. Guy Savoy aims for the same thing, but I have no first hand experience.