Here's my AFAIK personal scientific insight:

There are a few things that water's unique properties contributed to life on Earth.

1) Triple Point: Water's Triple Point is within the temperature ranges of the Earth. Had the Earth's orbit and tilt been different and bumped us into a colder or warmer regime, we would not have the benefit of vapor, water, and liguid which undermines all macro-life on Earth.

2) 4 degree anomoly: due to the molecular structure of water and a "quirk" in the van-der-waal forces, water's density is greatest at 4 degrees and thus ice floats... which is critical for aquatic life.

3) Molecular Structure: as noted before, water is quite unique in being a universal solvent as well as it's bonding characteristics. This is another reason why a helium doesn't seem like a good replacement for water as it lacks the complex molecular behaiviour that leads to 1 and 2 above.

4) Material Abundence: all of the above doesn't matter if there isn't enough of this base material to go around. The high percentage of water to land surface area, leading to oceans, leading to atmosphere, is also critical in water's role in life. Once again, a single gas like Helium would be a bad candidate for water substitution since it is only abundent on gas giants (which makes all our rules of evolution suspect) and not on rocky planets (since it would evaporate away quickly).


So, if I were to look for "other" life on "other" planets, I would start this way:

1) What is the planets temperature range and are there any Triple Point molecules that we know of in that range?
2) If yes to 1, is that molecule found in abundence in the planet?
3) If yes to 2, what are the dynamics of this molecule precence in the planet (ie: what is it's "weather" system)?
4) If yes to 3, what are the molecular properties that would be relevant in this weather system?

And from Question 4 on out, we can start speculating on what our "other" lifeform would be like based upon the world-building exercise above.