Oh there are so many things that Cristeen said that I totally agree with. My approach was about you changing what you can ultimately control and that is yourself. I really and truly hope that DH has shown you around town and that he does do one or two things with you when you are there. I was operating from that standpoint and maybe he 100% does ignore you and if it honestly is 100% then that really is a problem and it needs to be addressed.
There are a lot of factors here and we would all need the whole story to provide any real help. If this has been going on for several years and you have always sat miserable on the couch then he has probably shut down that part of his brain because he's ticked off that he has to "deal' with grumpy wife when he is supposed to be enjoying the thing he looks forward to all year. Perhaps you started off in a great mood the first time you went but as you realized how he was acting, you started to shut down and it progressed from there. Either way, it's a cycle that does have to be addressed. As for his family, they will always be on his side and your mom will be on your side, as she should be.
I still believe that it is once a year and that time is precious for valuable for him and that should be honoured by you. My husband and I believe that in being servants to each other and by putting each other 100% first, the other will never feel neglected. It's the weirdest thing, (I have just realized this lately) if I am "super ridiculously lovey dovey sweet" with my husband (which is hard for me because I am not that kind of a woman), he rejoices in my change of behaviour and our life gets better- noticably better, significantly better. My DH has always been the sweeter and more patient one out of the two of us and I took advantage of that for years. Now I am changing my own behaviours and I am putting his needs way before mine and like I said, the weirdest thing has happened, he has put me first. Neither one of us feels misunderstood, not heard or unappreciated (as we did for years and years).
He DOES need to know what you are feeling and you have to be clear and concise about it. He will shut down if it's the "same old.... same old". What's the old saying, "it's 10% what you say and 90% how you say it".... that is very true, especially in marriage. If he continues this behaviour despite YOUR efforts to be sweet, understanding, graceful and loving to him AND after you have spoken your peace then it's time to get down to the root of the problem but I honestly believe (and it would make for a good experiment to pass the time for you) that if you did those two things, you would see a change this year. Remember, don't blame- use your "feeling" words.
Also- please think about this; Now that I have kids, I think about things very differently. If MY son brings his wife home once a year and he wants to see his BFF and play video games with the BFF and his own dad- I will whole heartedly back my son up. He deserves that time (as you have already mentioned) and I would feel a little mad at his wife for making him feel bad about that time. If this were Deacon coming home after not seeing you and DH for a year, wouldn't you want him all to yourself (whether that's "good or bad")... the poor guy is being pulled in every single way. He is yours for 95% of the year, he needs this time.
There really was no need for me to write this because I know that you have already decided to go and give this a chance but this is something close to my heart as my DH and I have been working through our own issues for years. I KNOW exactly what you are feeling- trust me! I cried alone in our bathroom at 3am a lot when I was pregnant with our first. Every marriage is different BUT every single person wants to be heard, respected and loved. That has been true forever and if we make our partner feel like that and ask that they return the same respect and we do this each and every single time there is a discussion (it's SO HARD to do) then our marriages will improve.
Peace and love :)