The Countach is the king of cool. It's unfair to even put it there.
For modern ones, Aventador all the way, followed by Murci, then Diablo. Lambo is one of the only manufacturers that makes me fawn for their new iterations more than the previous ones ALWAYS, as it's rare for me to like cars of long lineages based simply on "which one is newer".
However, to keep with my typical theme, the Countach trumps all, so the Great Granddad gets the top spot.
As for which one I'd rather realistically own and drive today in my life? Aventador without a shadow of a doubt. Even though it'll make me look like a complete showy douchebag to perhaps more people than it'll impress. I like more conservative and "timelessly themed" cars, but when it comes to Lambo, the louder the better.