Legos are not what they were in the 80's and 90's when we were kids. They are so much more restrictive now. 99% of Legos are more like model building then actually using your imagination to create something.
Ugh. I've stopped being a fan of legos for the exact same reason. The modern lego sets that I see at the mall are chalk full of awkward-shaped, specially-designed pieces that you can't do much of anything with outside of the provided instructions. It's less imaginative for sure.
But yeah... I do like me some Minecraft every now and then. And yes, you can definitely compare the two. Minecraft gives you a unique, infinite world made of blocks, where you can collect blocks, combine blocks to create new blocks, build things with blocks, and tear down blocks to place other blocks. That's pretty damn lego-ish if you ask me.