For sure CG is probably the best place. Any wine they have on the menu can be purchased by the glass - we really like that, it gives us an opportunity to try more than one wine - not to mention you don't get "stuck" with a bottle you may not enjoy. You don't have to eat dinner there - there is limited space at the bar as well as a few other places to sit and enjoy the view and your wine.
A couple of other places also have nice selections of wine. The Yachtsman Steakhouse (YC/BC) has a nice wine list and the food & service are very good (this is our favorite place to eat at WDW). Spoodles (BW) has a pretty nice selection as well. Additionally, there is Martha's Vineyard (also at BC), it has a pretty nice atmosphere and a nice selection of wines. We really enjoy the Belle Vue Room (the Lobby Bar at the BWI), the atmosphere is really nice (you can sit inside or there are nice rocking chairs on the balcony - watch the folks on the BW) and they have some really nice wines by the glass.
Of course, the wines in Epcot at each country offer a chance to try some that you might otherwise not get a chance to. The best "wine time" at WDW is the Food & Wine Festival at Epcot. There are more wines offered, than usual, and it is really a nice time. Cheers!