without question motivation trumps toys. The question is which kinds of toy can best help.
I grew up just like you... so I have a bias towards more open ended toys... and that does seem to resonate w/ my 5 year old.
Still he also just LOVES to follow the directions for a new lego toy. and that is very structured. (and only done once, so its expensive!!). Still as I think about it, all of these lego vehicles then go on to have a mad-max second life where they are partially destroyed and merged into new chimeric creations.
yeah open ended play does seem the best! (and most fun too)