Wines CAN be too alcoholic, boyo. The usual giveaway is a "hot" feeling when tasting such wines. The fashionable American wine writer, Robert Parker, gave high alcohol wines a big push in the 80s, and some Aussie producers pinned their ears back producing reds up 18%; that's the old standard for fortified wines. Wines over 15% present problems in quite a few of our export markets as they require extra certification that they're wines.
The usual problem with high alcohol wines (say, over 14.5%) is that they aren't balanced; they generally display "hot" characteristics and the fruit/acid/tannin notes aren't in harmony. The other salient point is wines with high alcohol aren't good for laying down as they quickly become flabby.
In my view the best red wines generally don't go over 14% alcohol by volume. Whites rarely get to this level, 13% is high enough for them.