The historic ownership of the Falklands is very difficult to establish with any certainty, although Britain's claim is rather weak.

However we currently own the Islands for two reasons:

a) We won the war. The fact that this victory led to the collapse of Argentina's military regime is a bonus.

b) The Islanders prefer us to any other suitors.

Much the same applies to Gibraltar only its proximity and genuine strategic value make it more valuable. The Goverment which gives up the Falklands may, if it is lucky, survive. I doubt the same could be said over Gib.