"Good Day" is a great song, I think, because the day it describes is a good day. Not a the best day ever but a solid day. The things that Ice Cube enjoys about the day are, aside from the fancy ride, things that people of similar lived experience could also enjoy: solid breakfast in keeping with a diet, performing well in various competitive events, solid sex, and late night fast food.
But what strikes me more are the negative statements in the song, the lyrics that focus on bad things that could have happened but didn't, all of which make the song topical and political in a way that makes the songs good-feel vibes still feel consistent within the dark, angry Predator album.
Particularly, the lyrics that stand out to me are the ones that focus on that make note of the violence in early-90's LA. (The Predator was released not long after the Rodney King riots, marking a particularly tumultuous time in an already dangerous city.)
For example, early in the song Cube notes that he "finally got a call from a girl I wanna dig out/Hooked it up later as I hit the door/thinkin' will I live another 24?" He may be looking forward to his hot date later but that enthusiasm, and the good vibes from the halal breakfast he just ate are both clouded by the constant threat of death. In Cube's own words from Hip-Hop Documentary in 1994 (around 6:15):
Death is something that’s always on my mind because death comes so sudden to young Black males. You know, I don’t know anybody who planned to die … So just living another 24 hours is my focus. You can’t really plan on what you’re going to do next month or this month. Just getting the day, making sure you stay out of people’s way who are fools, who will take your life. So that’s constantly on my mind.
Later in the same verse he notes that while driving that there "wasn't a jacker in sight" which would probably lead us to believe that he has been carjacked before. Another factor in this "good day" that is simply the absence of something shitty.
In the second verse he notes he "didn't get no static from the cowards" which is surprising because "just yesterday them fools tried to blast me," so Ice Cube is having a good day, but this is coming after one that sounds like it was, shall we say, comparatively weak. To end the verse, Cube then notes that, on top of the great day he's having that "nobody I know got killed in south central L.A." This is again, something you'd only bring up if it happened to you consistently enough to be a real worry, just like the car jackers, just like the police, just like his self-consciousness about his own mortality.
There's plenty of "Today Was A Good Day" that is simple pleasures, but what makes it a truly great day is how he was able to get through the whole thing alive with no troubles. In South Central LA, that's not as common as it oughta be. Even getting up alive is cause for celebration.
"Just wakin' up in the morning gotta thank god."