Things that don't make sense (v2)

Those are enemies though, not aliens. I mean sure you're fighting a Rachni, or fighting a Krogan, or Geth, or some form of husk, but that's all it is: fighting. That's just a gameplay mechanic, not an 'alien' as you could easily replace your opponent with a cardboard box, or a floating stack of hamburger meat and it would change nothing in terms of the gameplay. When I am referencing alien elements, I am speaking of the times when Shepard didn't have to run in guns blazing, when we as players were afforded the opportunity to interact and explore these things which weren't human that didn't involve us shooting it in the face. 

When viewing the content of the games in that light, then ME 1 indeed has the most to offer in this department: 

We get to talk to the Hanar and Elcor in a straight faced attempt to learn about them and their culture in ME 1, whereas in ME 2&3 about 90% of what little interaction we do get is just Blatso references or tongue-n-cheek advertisements for Elcor Hamlet.

In the first game we get to talk to the Rachni Queen, and learn more about her species and see that they are more than what 2,000 year old accounts depict them as. In ME 3 we get a complete rehash of the scenario from Noveria with nothing new done with their character. This is made even more frustrating when the background lore and codex entries about Rachni immunity (or enough resistance to it that it may as well be) to Reaper indoctrination, and the fact that newly hatched Rachni are capable of working on the Crucible with no instruction needed is just tossed to the wayside and completely ignored.

In ME 1 we get to talk to the Thorian; well it's chosen mouthpiece at any rate; and we get to learn a small amount of how this fungoid based species perceives other aliens and the universe in general. The only thing even close to this level of depiction would be the Leviathans in ME 3's DLC, but even then they are just the old personality that the Reapers had (Pre-Catalyst) in the first game slapped onto a fleshy Reaper skeleton; not much originality there.

Now it's true the nature of the Geth was explored in ME 2, but the seeds for that elaboration were planted in the first title, and while the Geth were just mindless robots to kill in that game, there was at least some notion of an alien intellect driving their actions. Of course all of that nuance from the first and second ME is quickly chucked out the airlock come ME 3 to make room for the tried and true boring tale of Pinocchio-bots wanting to become "real boys".


As for your second point, yeah the level designs were definitely better in subsequent titles, but I kind of enjoyed the bleakness of some of those uncharted worlds. Not that they were fun to run/drive around in mind you, but they hammered home the innate hostility of the universe, that things we find familiar; such as planets with hospitable atmospheres and conditions conducive to human life; were in fact a small, small part of a much, much larger whole. Essentially, ME 1's uncharted worlds had the underlying theme (to me) that humanity wasn't the center of the universe, whereas the later games moved more and more towards the rule of cool as a design philosophy.