Thank you all for your replies. I apologize for not jumping back on here sooner. In response to the question about who is making these sorts of comments - it seems to mostly be family members of my parent's generation. Which is interesting, because I have heard of mothers-to-be and brides having this type of attitude (of being mad if they aren't the center of attention), but I thought it was a relatively new thing.
I think going forward I'll just continue to show enthusiasm, and if people press, use something along the lines of, "I'm surprised you have such a low opinion of me."