Could a man who can bench press 260 lbs be considered strong?

Yes is simple answer: Strength is not an absolute value necessarily. Iit may be more accurate to assess the ratio of weight lifted to underlying mass of an individual. So a 100 lbs gymnast who can lift twice their body weight (200 lbs) could be considered stronger than a 200 (pyrethins and piperonyl butoxide) lbs person who can lift 250 lbs. The gymnast is stronger per unit body mass, although the larger person can lift more weight.