i have both skies and pso.
i was reluctant to get pso when i kept hearing it was only really worth it if you went online. well my friend picked it up before i did and i can say after having played it for about 7 hours straight my first day, i knew i had to buy it. yes its got more longetivity if you get it online, but if you also have a circle of friends who enjoy RPG's then you may be able to get by with just the multiplayer. everyone ive had play it with me (which is about 6 people) all like it and 2 have bought it. since i have a lot of friends i can play with, it doesnt get old for me. if you can hook some friends of yours into it with you as well and you know you can play it with them more then say once a month, then i recommend that. everytime i play this game, its usually anywhere from 7-11 hours i play it straight. yes, thats SICK but that shows you how much i and my friends like the game. we're far from your "gaming geeks" as well. i havent played video games like that since i was in middle school/high school. im lucky i didnt screw up this past semester at college with all the playing i did. so, DEFINITELY get pso if you know you can get people to play with you. the only bad thing is there is some minor slow down when it has 4 people on the screen. the forest area is bad, but the ruins area worked flawlessly. its all a matter of if your in an open area or in room with walls.
as for skies, its also great. but since you said you rlooking for multiplayer, then i cant stress pso enough. if you can, rent it first and play with a friend or two.