um im pretty sure every planet is different???
Yes, but there are a lot of planets SIMILAR to Earth. The only thing that really makes Earth capable of supporting life is:
1. A temperature between 0C and 100C at a good portion of the planet (not particularly rare)
2. Geological activity (very, very common)
3. Storms or comets that can introduce amino acids (both of which are pretty common, but this is arguably the most limiting factor)
Out of the 10
22 stars in the observable universe (pessimistic number, there) and one planet per star (VERY pessimistic), that's still a few septillion planets. Even if those factors apply to 0.001% of all planets (again, pessimistic), we've still got pentillions of planets with potential life. A pentillion is a loving huge amount of planets and the chance of there not being a single intelligent organism there is almost nil.