No, it is incorrect to say it is 'not correct' because of not taking the exchange rate into the equation.  Of course you are welcome to include that in your own assessment of yours or anybody else's investment but it is perfectly reasonable to make the assessment of an investment on the basis of the currency in which it was invested alone.  Would you think me 'not correct' in saying I'd made a good profit from stocks I bought in euros even if the profit was more than wiped out from a pound perspective by the exchange rate having changed?