it really depends on where the fight is. apocalypse has the power to take down the ff if its in an enclosed space, or open field with nothing in sight. but reed is really the only factor that makes me think twice. if he can get his hands on practically any kind of tech hed be a danger. give him a video remote and an electric razor and he will drive away the celestials. apocalypse is a genius, and hes good with tech, but he hasnt shown himself to be anywhere near as resourcful as reed.
apocalypse written well would be an almost unstoppable force, but hes never written well, and despite all his planning, all his celestial tech, and all his powers he goes down hard so some mutants with mosly average power levels. physically, hes stronger than the thing, and his energy attacks should take on reed and johnny. hed probably overwhelm sues forcefields with some crazy jackhammer/piledriver type arms. so if reed can devise something, or utilise tech, id probably say its 5/10, if its just a straight fight, apoc wins 8-9/10.