I would never comment on someone else's ringtone, other than to say "that's interesting". I think it's rude to comment on a ringtone, I wouldn't comment on someone's choice of jewelry I guess I think it's similar.
My phone plays Jingle Bells year round - I hear lots of things. I also have some specialized ringtones for others:
ex MIL - Addams Family
my kids - Jeopardy
latest fling - Baby Your Baby by George Strait
my brothers - Troubador by George Strait
best friends - Thank You for Being A Friend
my office - Attitude Adjustment by Hank Williams, Jr
I mostly get chuckles and I don't really care what someone thinks about my choice of ringtones. Surely there are more important things going on in the world...
I've heard screaming babies, dogs barking, loud bells, some type of alarm sound, etc., yes I find some of them annoying, but really to comment on someone's ring tone - how annoying is that!