The marathon is great race, and if you are aiming to run your first in the new year, it is a great thing to accomplish.
That said, you can also get a great sense of accomplishment out of running races less than 42.2 kilometers. To see what I mean, I highly recommend these two articles that praise the 5K:
- The 5K, Not The Marathon, Is The Ideal Race | FiveThirtyEight
- 10 Reasons the 5K is Freaking Awesome | Runner’s World
After reading them, I had a much greater appreciation of that race. (I think the same argument could be made for the 10K.)
As for me, I am a fan of the half-marathon. The only thing I don’t like about it is the name: it implies you haven’t done something great, when you have. Perhaps it needs to get rebranded as a 20K: not half a marathon, but twice a 10K!
Regardless of the distance you run, and how often you run it, enjoy your athleticism and take pride in it.
(Chart is a link to the image from the FiveThirtyEight article)
Smart People I Know 
I kind of agree with a rebranding of half marathon races. Often times, I hear people say “oh it was just a half” like they have failed at doing the full marathon or they are second best.
True! Even the way people sometimes approach a half marathon (e.g. doing it in prep for a marathon) harms the race. That said, I still love it and I am going to keep thinking of it as 21K race.