the simple ability to faze through stuff and warping persons to another dimension can't really cover all the requirements to place him the strongest. eg
feats of knowledge, power and destruction goes to madara bar non (PS, rinnegan and wood release)
feats of intelligence, skills, versatility goes to itachi (totsoka, yata, tsukuyomi, amatarasu and the fastest seal + chakra control)
feats of tactics, skills, quick thinking goes to sasuke (EMS, Inferno release and susanoo)
obito hads no susanoo but he does have skills but other than that fazing which is his best defence where as itachi has yata and warping a persons to next dimension is as cheap as itachi use totsuka blade to seal someone.
idk obito is good and i agree but on a serious note he can't be the best with only his basic techs
