Raised Conservative, currently belong to a Reformed temple, and part of an interfaith family.
We currently do the following:
Shabbat - candles, challah, wine and prayers at home for Friday night dinner
Rosh Hashanah - festive meal at home first night, go to shul all day, festive meal at a relative second night
Yom Kippur - shul and fast all day
Sukkot - build a sukkah in the backyard and eat it in 3-5 times
Shemini Atzeret - honestly, I’ve never been sure what separates this from Sukkot
Simchat Torah - if we’re not otherwise busy, and not too tired, might go to synagogue and dance. Haven’t in several years, but always mean to go.
Chanukkah - menorah lighting, latkes, and presents at home
Tu B’Shevat - nope
Purim - go to synagogue in costume in the evening.
Pesach (Passover) - seder at home for 1st two nights (one big with lots of relatives, one small), don’t eat chametz for a week.
Lag B’Omer - Never really understood what this one is…
Shavu’ot - nope
Tisha B’Av - usually don’t notice it until it’s past. Never do anything except maybe eat a dairy meal if I remember to do so.
I would guess that my “score” of about 7.5/13 is on the high side for my level of observance. Most Orthodox will probably say “all of them, and more minor ones not on that list”. Most Reformed will say Chanukah, Passover, RH, YK at best… maybe Purim. Most Conservative will be somewhere in between.
But I don’t think the idea of having more holidays than most adherents observe is limited to Judaism. Do most Catholics observe all of these:
http://www.calendar-12.com/catholic_holidays
? (for example)