I'm a Parisian and I think Marseille is an excellent city. Two days is good for a first taste of the city, but you will probably want to return.
I go to the Avignon festival every July for about a week, so I know the city (at least intra muros) by heart. I find it wonderful in July, but I quickly get bored if I go there any other month, but that's just me. In any case it is an excellent base for visiting the Luberon. Some friends met me in Avignon last year when I had had enough of the festival and we went to the Pont du Gard, Saint Rémy, Les Baux, Gordes, Mont Ventoux and all though the lavender fields. It was wonderful.