I have just as strong a bond with all my dogs. But it's a different type of bond. With Spud, he is very independent but loves to be loved anytime. He doesn't need you there, but if you want to be around him, he really likes it. Precious is needy. She is very needy and puppyish and just has to have love all the time. Roxy is of course around me all the time since she is a toy dog and has to stay inside. Spud would be very left out if we didn't work at it. Precious is very pushy for attention and Roxy likes to be in the spotlight while Spud will sit in a corner and watch from afar. I try very hard to have an equal relationship with all three of them and not making any of them feel left out.
I guess it really depends on the personality of the dog. You just have to work at some harder than the other while making them all feel equal.