Greenland, New Guinea, Borneo, Madagascar, ?, Sumatra, Honshu, Great Britain

All of these are Islands....

And the sequence cannot be the number of Medals won at the olympics... or is it ?... The other way round...GB wining the most and Greenland the least

Could also be the population...this makes sense...as Greenland would have the least and GB the highest... ( I think !)

But all this still doesn't give the mising value !!!