Value and drinkability of vintage wines

[Les]

My first interest of course, is...are the wines I have drinkable and even worth opening? Or are they valued higher unopened, even though they may not be drinkable?

So...I have a Silver Oak 1986 Alexander Valley Cabernet Sauvignon, a Cakebread Cellars 1990 Napa Valley Cabernet Sauvignon and a 1992 Cakebread Napa Valley Cabernet.