A Your baby is lucky to have you! Through your sensitive nighttime parenting, your son is developing a healthy attitude about sleep. But there are few easygoing, mellow babies or toddlers who can be put down while awake and comfort themselves to sleep; realistically, most children under the age of 2 want or need to be "parented" to sleep.
You mention that you feel this is a "habit." It's oftentimes difficult for parents to tell a need from a habit, yet in my experience habits are easily broken, while needs are not. Toddlers normally have difficulty winding down and succumbing to sleep without a bit of parental help. If your child protests going to bed by himself after you've tried all your usual bedtime tricks, consider it a need rather than a habit. Also expect your son to draw out the going-to-bed ritual if you work outside the home or have been away from him a lot that day. Children see evenings as a prime time for being with their parents, so they'll do all they can to put off going to sleep. Be prepared for the stage about a year from now when your child pleads for you to read the same bedtime story over and over.
That's why it's wiser to think long-term. The rituals that you create now to help your child go to sleep will help ensure better sleep for everyone in the family when he is older. But rocking your baby to sleep isn't the only routine or prop you can use. In getting our children to sleep, Martha and I have used a variety of parental props to shorten drawn-out going-to-bed routines. Some to try: tape recordings of your son's favorite lullabies; the tick-tock of a metronome set at 60 beats per minute; a bubbling fish tank; or a cuddly teddy bear he chooses just before bed. But if your son still absolutely won't go to bed without rocking with you or your spouse, consider this to be something he still needs, and try again in a month or two.