2003 is my favorite which was the 25th anniversary special. It was very cinematic in an epic but beautiful way, and told the origin story of the first IM.  2004 is in a close second. Both really played up the idea that Hawaii is a mythical place and that this gathering of ordinary people doing something crazy was even more mythical. 2004 even personified the spirit of hawaii in the form of a little girl dancing in the black lava fields. I'm a film nut, so I really appreciated the effort that they put into the cinematography. I love triathlon, but even I have my limits of just watching people ride their bikes for hours on end, so it was cool to take something otherwise mundane and make it very dramatic. After that it started going down hill for me and the production value seemed to get cheap, and it just started becoming- "And then this person was in the lead....and then this person...and that person's in the lead now..."  Not that they suck, I still watch them every year, but '03 and '04 were the cream of the crop. Watching Marc Herremans slowly push his wheelchair up the hills in the darkness tore at my gut, and (SPOLIER) watching Sarah Reinertsen miss the cutoff by 15 minutes is enough to make a grown man shed a tear. 

1982