Lego, since athor building blocks what I have seen doesnt have sutch HUGE variety betwen different parts!Really, there are thousands, thousands and thousands different lego parts.
lego's are obviously more superior! close second is k'nex though, because they got some cool roller coaster sets. but megablox is a definite last, because the blocks don't even stick together.
When I was little, I always enjoyed building lots and lots of stuff out of Lego's....... I believe one time i built an entire battlefield populated with plastic army men, though my blocks were semi-outdated and the color scheme so terrible it looked awesome...heh, those were good days.
Oh my God what a mad thread! I'm sold out to Legos and K'nexes. Studies have shown that children playing with legos and such will have an easier time developing a sense of logic and a more fertile imagination, thus, my kids are going to play legos, whether they like it or not.
I had that humungous, 5-foot tall k'nex ball tower when I was young. The good old times...
Meccano is a British invention, and thus hasn't spread quite far sadly. I myself haven't had the opportunity to get my hands on much, but it sure looks appealing.
seriously though, erector sets are awesome. then come legos, k'nex, lincoln logs, and finally, megablox. the blocks that can't stay connected with one another no matter how hard you try!