I swear, I can't think of a movie wherein Keanu Reeves isn't just "Keanu Reeves," but I love most of his films.
Yeah he doesn't have a lot of range as an actor. I do think that movie shows a lot more emotion from him, as he starts to mentally break down due to the data leakage in his brain. It's usually in tiny bursts of anger/frustration, like when he snaps at Jade a few times in the sewers, to his "I WANT ROOM SERVICE!!" scene, which I still think is genuinely fantastic. But he also has some fun banter and wit when he's flirting with her when he's taking her phone card to call Pharmacom.
I think, the way it just melts down, and he deflates is just amazing. Most people who talk about that scene, just see it as some entitled rich guy having a tantrum. But, I think there is more going on under that scene, and it's entirely due to Keanu actually putting in some emotion work. Yes, he is finally losing his shit and bitching about the complete unfairness and insanity that has been his life for the past 24 hours. Up to, and including having a fucking volkswagen bug explode and dropped onto him as a bomb. His brain is literally dying in his head, hurts like hell (something Spider points out), his sanity is slipping, his ability to control his body is failing as he has increasingly powerful seizures, and all he wants is to just get the data out of his skull.
He doesn't want to be down in the slums, fighting rats and newspapers. He wants the life that he had, was comfortable with, until less than a day ago, when one asshole fucked him over, and set him up to die. But the part that I think is kind of lost, is at the end, when he's starting to lose his mania, and is like "I want my shirts laundered...like they do...at the....*kind of pauses like he's having trouble remembering* Imperial Hotel...*slumps to the ground, mentally and physically exhausted, wondering if he's literally going to just die on a pile of trash next to a filth infested river in the ass end of Newark* "....in....Tokyo" I think he's trying desperately to just hold onto the fraying vestiges of his old life, and his mind, memory, any of it. But, second by second, it's all fading, and he also has to try and fight off combat squads at the same time. But...he just can't do it anymore. He can't keep his composure. He loses it. And I don't think this is just my headcanon about it. Because Jade's response to his rant, isn't to call him on his BS. She clearly shows signs of empathy, and compassion for him. She goes up to him, and sits next to him, realizing what's going on in his head, and how it's effecting him. And she tries to show him some comfort.
I honestly think, it's probably one of his most emotive performances ever. It felt genuine to me, in the context of the character and film. I fucking love Johnny Mnemonic.