I can't imagine not playing ME2 and ME3 after ME1, but while I enjoyed ME1 quite a bit, it was my least favorite, so yeah. Also, I'm really OCD about following an entire story, too, so even if I liked 2 and 3 less, I'd probably play them. Then again, ME1 does end somewhat neatly -- Shepard going off to find a way to stop the Reapers is a marginally OK bookend, I s'pose.
And yeah,
Skywalker, that other book totally never happened.

I actually contributed to that infamous Google Document a few times and "held the line" with the threads drawing attention to the travesty on BSN, so believe me, I fought the good fight against that horrible sequel. Now THERE'S a
Mass Effect product I won't go near again!
I love it when Shepard calls Kai Leng out for how pathetic he really is -- I think THAT'S the reason the dynamic still
kinda works for me, because he's really not supposed to be the even-keeled nemesis like Saren was, he just
thinks he is. Is that nearly as cool? Nah, but I'm OK with it.
And technically Kai Leng was "introduced" during the Mars mission, if you wanna stretch things quite a bit and say that seeing him standing next to The Illusive Man counts. But, haha, yeah, I know what you mean and I agree. He could have bailed when he recognized that Eva Core was screwed, or something, but maybe temporarily trapped Liara and barked at her over how much he hated asari. You know, something "superfluous" which actually enriched his character beyond "I hate you, Shepard".