Chris, I think Manhattans are better balanced with a 2:1 ratio of whiskey to vermouth, rather than the 3:1 suggested here. I also like them with a bit more syrup from the cherry jar -- maybe a barspoon. I don't know what you were using for ingredients, but better ones will of course make a better drink. No matter what brand of vermouth you use, it needs to be fresh. Vermouth goes stale after a few months once it's opened, even if you keep it in the refrigerator.
Sorry for the late response. Absolutely Scott, good ingredients, better drinks. The vermouth was less then 3 months since it was opened. Sadly, 2:1 was even worse. Maybe I just don't like Manhattans, or very spirit forward drinks in general. I guess it's sort of normal, considering I'm only in my early 20s.
A lot of people prefer carpano as the vermouth. Could make the difference for you. Sweeter and more full bodied. You could try one in a bar before deciding to invest in the big bottle. Rye and carpano is def a favourite for me.