For me I still think it's Morales - Marquez' style just happens to be great against Pacquiao, but there are other styles which pose issues for Marquez. I'm biased anyway as Morales is one of my all time favourites but still think he has to get the slight edge over Marquez
I think they're equal in legacy, really. Barrera and Morales fought much better opposition in the first half of their careers at super-bantam, featherweight and super-featherweight (when both were a little past it). Then again, Marquez is the only one who didn't get steamrolled against Manny and his longevity also counts for him. As for his victory over Pacquiao, it sure was impressive, but i really think Manny is past his best, against Morales, Pacquiao was in his physical prime (not in his technical prime tough). H2H, i think both Barrera and Morales could beat Marquez. Barrera was past his best and gave Marquez a very hard fight, had that fight happened in 2002-2001, i think it would be a different story. Barrera made Marquez fight off the front foot, using his jab very well to find oppenings to counter inside. Morales had that tendency that, whenever he got hit he would start to brawl, that would play better Marquez hands (but i also don't think Marquez could stand go toe to toe against Erik). Erik's size and reachs would trouble Marquez and make difficult for him to counter effectively, Morales wouldn't have to reach in like Manny to land his punches, i also think Morales would have an advantage in handspeed. I think Morales edges him on a unanimous decision.
You put these names in a bag and draw one out and there's really no bad selection. I'm biased as I think Morales at his best was very ,very good but his style hurts his longevity. Morales and Marquez would have been a great one