Believe me, Scheer, I know exactly how that situation feels, and it is nowhere close to fun.
First of all, the most important and necessary things to do, is to be as patient as you possibly can, and make sure you talk to him. It's likely he may not understand, simply because this dog is obviously something he really feels he needs, and you need to be able to recognize that. That doesn't mean it makes it any easier for you, and it doesn't excuse him for ignoring you, but if you love your mate, it helps to be supportive of what he wants - especially if it's important to him. It's unlikely that he loves (or likes) you any less because he got the dog either, even though he obviously may not be showing it very well.
I would definitely talk to him about maybe putting the dog through obedience training, if possible. You two could also try to work out ways to see each other more often, such as letting another friend watch the dog for a while some days or something. Perhaps you could offer to put more time into helping him care for the dog, in a way that you'd both be working on something together, rather than you just following behind.
This dog is also very new to his house, obviously, and animals do often take a little time to adjust to new places. The dog may be better in a relatively short period of time. So, again, it is very important to be patient to see if things continue on this way or if they revert back to the way they were.
And, in the end, you two may just have to agree to disagree. It happens sometimes. It's hardly a good idea to break up just because things get a little rough, unless it's something that you're positive you can't get through. Sometimes life just gets in the way. It happens. My mate and I only get to see each other once every 2-4 weeks during the school year, and it gets incredibly tough after spending nearly every other day with each other during the summer, but we still manage to persevere. It is possible, if that's what you want. Relationships aren't just filled to the brim with roses and candy and happiness.