The question regarding "champagnes" from other countries leads me to make this statement. A true Champagne (from the Champagne region of France) is hard to compare to sparking wines of any other country. The quality of true Champagne is so far and above anything else out there... an area where efforts from other countries just don't match up.
I think that when it comes to still wines there are countries that product world class efforts... some of the best reds or whites (mainly reds actually) in the world. Say Vega Sicilia or L'Ermita from Spain, Sassicaia, Masseto, Gaja from Italy, of course all the great Bordeaux, Burgundies and Rhones from France, Harlan or the like from California, etc. (and the same is true regarding the less expensive wines from these regions).
When it comes to Champagne, nothing comes close. Agree, or does anyone want to challenge that statement and suggest a sparkling wine they think DOES equal a fine Champange?
(P.S. - Leave out the price/value argument... ie. I'd rather drink X at $20 a bottle than a French Champagne at $$50... that's a different discussion).