There are quite a few contenders for the best Jewish holiday. Some you can dress up, at most you drink, at all of them you can eat good food. Which do you like the most?
http://www.ranker.com/list/the-best-jewish-holiday/jewishvlibrary,
Simchat Torah
You don't go to work and you get to dance with the Torah, which doesn't happen every day. If you've never given Simchat Torah services a try, we suggest that you do so at least once.
Passover
Did you know Jews are commanded to drink four cups of wine on Passover? Four entire cups. Combine that with good food and family and you've got yourself
Rosh Hashanah
It's the Jewish new year! You get to be written into the Book of Life, hear the Shofar blown, and eat delicious home cooking. Not bad!
Purim, The Feast of Esther
Purim is the Jewish Halloween! You get to dress up, drink as much alcohol as you want, and if you go to synagogue there's a hilarious Purim spiel.
Shavuot
Shavuot's an important holiday, as it celebrates the deliverance of the Ten Commandments. Sure it may lack the branding of some of the other holidays, but Jews are commanded to eat dairy foods like cheesecake and blintzes, and stay up all night. Can Tu B'shevat say that?
Hannukah
The most Americanized Jewish holiday so we're sure you're already familiar with it. Presents? Check. Fried food? Check. Gambling with chocolate? Check. And it lasts eight days!