2 year old question to ask?

ok, so my son just turned 2. For the entire time of his life, he has been really difficult putting to sleep or falling asleep. Once he is sleeping though he is a great sleeper. My frustration is that in the last week (and this has been happening for a long time now) - we have a night time routine, which is usually, change diaper, change into p.j's, quiet time and read books with mommy and daddy, then bottle in room and crib. I will have to sit in his room for over an hour until he falls asleep and sometimes he won't! and it will be hours, and hours!. Which is not good for me because I have a 6 month old baby too and I am loosing my sleep because he won't sleep. My husband on the other hand will do everything to cater to his needs. Lately he has been helping me, but he crawls into our son's crib and will sleep with him until he is fully asleep. Now, that's fine, although our son won't fall asleep until after 10pm and then he is exhausted the next day!. Last night, he woke up suddenly and saw that daddy wasn't there and started to cry. I went in and sat in there for almost a hour and he still wouldn't sleep but he would sit in his crib and lye down without crying, so I knew that he wasn't sick or scared or anything. So after an hour being 3 in the morning I let him cry for 10-15 mintues which I have never did! and sure enough he stopped and that was it. Is that what I should do from now on? Let him cry a bit...it seems to work well or at least for this time anyway. We just checked him at the doctor last weekend and he has no ear infections or anything. Any advice would be great. Sorry its so long. Thanks.