I started smoking cigars because they made me feel like a man, and like a big shot or something--important, rich, etc. I was 18.
About 2 years ago I started getting a lot more serious about cigars when I discovered a few that had really great flavor ... the stick that "pulled me back in" was Don Pepin's 5 Vegas Miami. Ironically, I don't much care for that stick these days, but tastes vary over time.
So for me, I got really into cigars because of the great flavor, and since then have come appreciate all the other aspects. 2ndary for me now is probably the physiological and psychological effects of a cigar, meaning both the "drug" itself as well as the placebo effect of calming and relaxing that have come to be strongly associated with a cigar for me. Aroma would be last ... I try not to breath the resting/2nd-hand smoke at all, so it's rare that I think "wow, this cigar has a great aroma." I did have that though when I smoked my 1st/only Cain Habano the other day--it smelled like a "man's cigar," though i'm not even sure what I mean by that.
But even so, if I have a cold or something (like now) and know I won't be able to taste a cigar, I won't go out and smoke anyway ... so flavor is clearly #1 for me.