Thanks to all who have contributed their thoughts and opinions so far. I am going to let this initial stage of discussion and nomination thoroughly run its course before moving on to the next step, and I hope that many more weigh in before then.
At this point I am getting the sense that it would probably be better to develop a set of categories (hinted at by
@Dan Robinson 's post) to eliminate the difficulty with distinguishing between which qualities make one event better than another. I think the following broad types of categories may work:
-meteorological significance: severe report count extremes, seasonal/geographic/diurnal anomalies etc.
-scientific significance, e.g., measurement extremes
-aesthetic qualities: most photogenic, most thoroughly documented, best available videos
-human impact
-miscellaneous, e.g., unexpected events, overperforming events, events outside the typical tornado alley
Feel free to suggest specific categories as well.