why aliens come to earth?

For hot chicks may be but they may be coming to earth to enjoy slow paced time.
Earth was made for us to live and we breath Oxygen and we have suitable weather but for aliens it may not be suitable so they wear some transparent glassed helmet to breath or puke :p i have never seen aliens but watching Alien movie made me believe that alien breath some thing other than O2 .

may be the creator doesn't want other living being leaving their planet and living on other planet

why aliens are more intellgent than us?

It been proved that when we go far from earth the clock ticks faster which means times goes away quickly like traveling in future

NASA has performed this experiment by putting a clock in rocket and one in there station,when the rocket launched it's been observed that seconds hand was ticking faster with respect to increase in distance from earth

In earth due to gravity we have a time at slow pace which help's us in development
but Living things which live on some far away planet aka aliens who may be on non-gravity surface may experience a quick flow of time .which means there development is quicker than us and more development means more advanced sophisticated tech and intelligence.