I never said he possessed powers like Magus, etc., what meant was that he was experienced in the field of sorcery (such as creating a potion for immortality, which was ill-fated for Owen's forearm). Anyway, I stand by my answer as Xanatos being more intelligent than Lex. I mean, he used his wealth towards something truely remarkable, such as hiring a scientist to create a successful cloning project. Also, Lex may have designed a suit that could hold its own against Superman, though it relied heavily on its own powers, while Xanatos's suit required him to be a skilled fighter, otherwise he wouldn't have stood a chance. It may be considered that he's smarter because he designed better weaponry, however, designing just what was necessary not to be killed, and then using your own physical powers makes for a much better mastermind. Put Lex in the Gargoyle suit, and he'd have been killed instantly by Goliath (assuming it was a fight to the death, anyway). That's what makes him a mastermind. He definitely had the power to create a suit that could have instantly killed Goliath, or simply crushed him while he slept (which is what Lex surely would have done in his position), though he wanted the satisfactory of killing him when his opponent could put up a fight.
Also, about your statement about Ras Al Ghoul being the "true mastermind", you obviously haven't read the Spider-Man/ Batman TPB in which Ras Al Ghoul is out smarted by The Kingpin, whom no one even considers the "true mastermind". ^o) Even further into that statement, it's pretty cowardice to try to take over a place where you can't even be prosecuted for your crimes; he's got diplomatic immunity, so he's carefree his plans being stopped, as even if they are, he's still a free man. Xanatos takes risks every day with the evil deeds that he performs, as if he's caught, he's certainly going to jail. That's what makes the two so intelligent -- sure, they can be sent to jail for a life sentence in some cases of their crimes, however, they are so smart that they don't even consider failing as an option. In my opinion, Lex is a better mastermind than Ra's Al Ghoul.