why do men tend to be understated?  

We are individuals with different personalities and characteristics. I presume that you already know your boy friend very well for that two year relationship. I guess that simple "thank you" word as an answer would already mean a lot. He just can't extremely express it out unlike the others you have normally expect to do.

..hi.. well, men have different personalities and I think he is grateful with what you did.. he just can't find other things to say but a plain thank you.. and I guess that two words mean so much actually.. it summarizes everything that he wants to tell you so don't get disappointed.. I believe he has his own way of letting you feel that you are appreciated.. maybe not in words but through his actions.. Most men are not really that vocal.. My husband isn't.. he just show it in his actions..

I could make guesses, I think he liked it but only a little, I mean, I'm sorry to tell you this but this is just my opinion anyway - because if he liked it a lot, he could've responded in a more cheerful way and you could've seen it in his eyes. well, hope i'm wrong on this one...