Ok, I'll take a stab at this one. I know infjs are notorious for not finding love, happiness, comfort, etc. And entps are supposed to be very compatible. While personality typing is not everything, and we all know that if you locked a thousand infjs in a room, you would have a thousand different personalities, I have to agree that entps are very compatible with infjs, perhaps most so than any other.
I say this b/c my high school bf was entp, and my husband of 13 years is entp. Other boyfriends I have had have not lasted long at all. The only two long term relationships were the only 2 entps.
Now as to why this is, I am not sure. We seem to make up for each others shortcomings. I boost his F, he boosts my E, we learn from each other, and rather than polarizing b/c we have differing traits, we somehow meld, like two puzzle pieces. We bicker, but we rarely fight. We keep each other grounded. We communicate well... it is a tough thing to explain, and I seem to be very in-eloquent tonight.