Extraterrestrial life is I think highly probable. It's decently possible in the solar system. Unfortunately, one planet we increasingly believe WAS a pleasant place for life to arise - Mars - is now dry and almost airless.
Europa is a possibility, but the chemistry of its suspected ocean could turn out to be all wrong. Titan's an outside bet, it's probably too cold. Io might seem outlandish, but it's got plenty of heat and sulphur, though I'm not sure there's a viable solvent for life.
Beyond the Solar System, it may be decades or centuries before we become able to carry out the kind of exploration that would be needed to definitively confirm the presence of life. However, detecting reactive chemicals in planetary atmospheres (most obviously oxygen, but any reactive chemical would do) would be a very strong indicator of life - though it would be hard to categorically rule out physical processes.
Of course there's SETI, but we've been listening for decades and heard nothing definite. Extraterrestrial intelligence is almost certainly much less likely that life, since judging from life on Earth intelligence requires massive costs and is thus usually not evolutionary advantageous. It's also suspected intelligent species are liable to self-destruct through war, and a species usually only gets one chance at developing civilisation, since the developmental route will use up the easily-obtained resources, leaving only those which require a functioning advanced civilisation to obtain them. If humanity lost all its modern machinery, we'd have trouble obtaining decent amounts of iron ore for example. Once advanced civilisation falls, whether through war or natural disaster, it is unlikely to recover and the species will go extinct.
If intelligent aliens do exist, I think it is rather likely they would be somewhat hostile. It seems reasonably plausible an intelligent species would seek to wipe out other species for no gain, or for territory, since the same behaviour has been exhibited by humans against other humans numerous times in history. It's also very likely we would be unable to oppose another species seeking to exploit our resources in manners detrimental to us. We can probably take consolation from the fact that it's not clear what Earth has over other planets and moons that would make it particularly useful to extraterrestrial life; biological differences would likely make us useless as alien food (and vice versa), most metals and minerals are probably easier to get from a body with lower gravity, and even water can be had in ample abundance in the moons of the gas giants. Coal and oil are probably found in the Solar System only on Earth, but unless the aliens own planets have similar materials why would they want them?
Of course, we do know where to find stuff on Earth. It's unlikely any species can just remotely scan a planet and know the resources it has. Commandeering our own mines and quarries would be much quicker.
One should not assume that for aliens to reach us they must be vastly more intelligent than us. Technological progress is a very different thing to intelligence - the former is cultural and advances rapidly, the latter strongly biological and likely advances more slowly. Technological development could be driven by a "long tail" of genius individuals in a species generally much less intelligent than those individuals. So while it would be no surprise to meet aliens with IQs of 200, it would also be no surprise if they turned out to have IQs of 70.
