For me it was in 1968, a trip to the BWCA, as a reward for working at a YMCA camp in Wisconsin for the whole summer.  A few trips here to the BW over the years. Until I moved to northern MN in 2000.  Then I began tripping to the BW 4-5 times each summer.
I began to feel crowded with all the people so, in 2005, I did a solo trip to the Q.  Wow, what a difference, saw only two or three groups in 5 days.  I thought that was great.  Also, a trip to Atikokan is the same distance as Ely for me, so I have a choice.
I began reading about WCPP in about 2009, and did my first trip there in 2010.  I have found I love it up there.  Why?  Probably the solitude, fishing and the remoteness, all strike me as what I'm looking for.  Last year,I didn't get to go, but have two trips in the works for this year.  I will be going solo for one of the trips, and may take a friend to introduce him to the area.  Though I now prefer solo trips.
All the areas have something to offer, but right now, WCPP is my favorite.  I get the true feeling of wilderness up there, and sometimes its difficult to find the portages.  I think its the feeling of being totally alone that intrigues me.