You've written "obviously he is getting too old and too big to be getting in a baby swing every night," but I'm having trouble understanding why that is so obvious. Is it because he's actually getting too big to fit into it? It sounds like he still finds it comfortable. You mention that it's well made, so apparently his safety is not at risk. So I guess I'm wondering whether your reluctance to let him keep up this comforting ritual is based on some physical fact, or the idea of a "baby" swing, or the idea that it's a bad habit. I really wish you could explain why you find it a "bad" habit.
If all moms of sleep-resistant babies could find such a sure-fire, and relatively harmless, way to help their little ones unwind for sleep, I'll bet they'd jump at it. Your little guy is unwound and ready for sleep after half an hour in his comfortable chair, so much so that you can even put him in bed awake. That would sound nearly miraculous for lots of weary moms of poor sleepers. Since I don't understand what your objection is (maybe you have a really good one), I'd say let him keep the swing ritual until he can't comfortably fit in it any longer. An older child is usually easier to reason with, not harder.
I'm actually more interested in his watching canned entertainment before bed. Are you certain that at least part of the lure of the swing isn't that he also gets to watch Elmo? There's a fair amount of research into brain patterns that suggests TV is stimulating, addictive, and counterproductive to good sleep. If he's only getting half an hour a day, and his sleep is normal, there's apparently no real harm being done. But I'd be watching for a growing need or demand from him for more screen time, and the onset of sleep difficulties or nightmares, just in case.
If you are committed to getting him out of the swing, how about not making it a cold-turkey double loss for him all at once, since sudden losses can throw a toddler's sleep AND behavioral patterns off. Try allowing the swing but cutting off the tube, for example. Maybe you could read a book or play music for him while he swings. If he makes that adjustment for a week or two, try reducing the swing time by 5 minutes a week. You might be able to ease him out of this routine with relatively little stress for either of you.
Finally, look at what Dr. Harvey Karp does with toddler wants and demands in a series of interviews regarding his book The Happiest Toddler on the Block. He empathizes with demanding, crying, whining or tantruming children, emoting right alongside them, until they recognize he understands their expressed desires. This is very calming, and then the parent can introduce alternatives that the child can better hear. I have found it to work well with a number of small children I occasionally work with. Start with this video, then check out other related ones and see whether this helps you and your son:
http://www.youtube.com/watch?v=fJ1428uYs2g&NR=1&f...