The Mass Effect series introduces players to a wide range of alien races, many of which are distinctly different from humans in terms of appearance. Others, though, aren't quite as unique. Mass Effect 4 has the chance to bring new species into the series, and BioWare should take the opportunity to create stranger and less humanoid designs for players to encounter.
Aliens in the Mass Effect series can effectively be divided into two categories in terms of their importance to the overall narrative. The Council races are those that hold a seat of power on the Citadel, and as of Mass Effect 2 includes the asari, turians, salarians, and humans. Although other races do inhabit the Citadel, such as the hanar and the elcor, they aren't as prominently featured in the politics of the galaxy nor the main storyline of the Mass Effect trilogy. There are also a few outliers who don't inhabit the Citadel whatsoever. For example, the vorcha and the bararians instead often appear as cannon fodder during combat missions, though there are some exceptions.
A recurring trait among the more commonly featured alien races in Mass Effect, though, is how humanoid they are. This is especially true of the asari and the quarians, although Mass Effect Legendary Edition changed this in part when BioWare altered Tali's face reveal. Especially in Mass Effect 1, a large number of background characters are asari, which look almost identical to humans save for the coloring of their skin and the fact that they lack hair. There are multiple asari and human crewmates in Mass Effect, as well, as opposed to only one turian and salarian.
Mass Effect 4's Range Of Alien Species Needs To Be Wider
Not all of Mass Effect's aliens so closely resemble humans. Krogan are much larger on average than most humans in the series, and frequent references to their biology makes it clear that they're distinctly unique even among the other races of the galaxy. One such example is the fact that they have redundant copies of most major organs. Leviathans, the giant species responsible for creating the Reapers, resemble squids more than any humanoid creature. Likewise, the hanar are often compared in-game to jellyfish. Unfortunately, many of these stranger alien designs appear almost exclusively among Mass Effect's most underutilized alien species. Although the elcor and the volus both appear frequently on the Citadel in Mass Effect 1, they don't serve as crewmates or even major characters throughout the rest of the series.
Mass Effect: Andromeda did bring a couple new species into the galaxy: the angara and the kett. However, both were relatively close to humans in terms of appearance as well. They're bipedal, of similar size, and their facial structure resembles that of the asari. Beyond those two additions, every other alien featured in the game was one of the Council races from the Mass Effect trilogy, with the exception of the krogan. While this limited variety may have been due to Andromeda's budget constraints, it still fell disappointingly short of player expectations, especially given how many new species fans were invited to learn about in the first Mass Effect game. Hopefully Mass Effect 4 takes steps to properly bring a wider range of strange aliens into the world of the series.