I caught this one last week on demand and enjoyed it. The main character reminded me of a Polynesian Kevin Kline. I liked how it was a satire that didn't fall back on the stereotypical ploys of caricature in most of todays movies. It ended up being a pretty well grounded, funny and humanistic take on the subject of 'what goes bump in the night.' For some reason I couldn't stop laughing when they had killed that vampire hunter, and Viago said 'his soul is in hell' to the mind-tricked police when they came over and saw his corpse.
I don't think I watched the original trilogy until I was 9 or so - but wish I could have sooner. Granted that was 20+ years ago when spoilers could only come from friends, etc... I'm not sure I could appreciate it as much at a younger age, but it's a whole new frame of mind these days. Inimicus nailed it right on the head. If he's more into the story arc then show him the importance of Kenobi to Luke and to Anakin and how that pans out throughout the movies. I'd personally watch 4-6 then 1-3 to grasp that, but a case can be made for both sides.
The visuals are a bit tougher to get over unless you know about the time difference between releases.
Sorry I couldn't be of better help, but I would be curious to know how he would rank them after seeing all 6 :) My (sometimes changing order) seems to go 5 - 4 - 3 - 1 - 6 - 2 (Yeah, I liked TPM more than ROTJ)