Gameplay >>>>>> graphics
You do need a minimum level of graphics to be enjoyable though. Just throwing out an example, for an RPG, you'd want Infinity Engine-level graphics at the worst, for a rich gaming experience.
Fukumoto's art passes the minimum quality requirement for a manga.
For an example of what doesn't pass, see HxH at the start of the chimera ant arc. Thank God that the guy is putting in more effort now.