When Voyager 1 and 2 crossed the solar system, discovering one world after another (33 all told, I recall), it led people to realize hoW different those celestial bodies were from each other. There always were surprises, no matter how close they were from each other, they still were so different.

Now that alien stellar systems are discovered, with their courts of planets, the same seem to be the case. All those systems are so different from ours.

But this might reveal more about ourselves and our lack of imagination or even our urge to find earth-like planets (or Mars-like, Jupiter-mike) everywhere.
Is it really that important to find an Earthlike planet, or is it a remnant of our imperialistic culture?
I wouldn't be astonished if our descendants decided (slowly) another space-related quest became a priority rather than life or Earths elsewhere. It would depend on lots of things (like previous discoveries, or culture, or a major dramatic event).
The nice thing about discovery IS the surprise!

Raoul