that truly mastering Spanish with all the nuances and subtleties takes that much less time than doing the same for Portuguese or French? I would agree that basic Spanish is easier than basic French and Portuguese, in the latter case for pronunciation reasons if nothing else, but if we're talking learning a language to the point of approaching near-native level in spoken and written language, I'm not sure there's that much of a difference. Some of the trickier points of the grammar - use of the subjunctive, use of the past tenses - are comparable in Spanish and French (and I would assume Portuguese), and Spanish has the additional hurdle of having so many different regional variations - even if you restrict yourself to learning one of them, you still have to figure out which words or structures you can and can't use.

Of course, Tibetan, Akkadian and other non-Indo-European (or more distant Indo-European, like Albanian or Baltic or Indo-Iranian) languages would be a very different story.