I think the fact that you've never watched Family Guy before might really mess with your perception of the episode. Not saying you have to like it, but a lot of what Family Guy does will end up lost on you and potentially annoy you. As someone who's seen almost every episode of the show, this is a typical episode featuring Simpsons characters. It's nowhere near the worst episode. But it doesn't sound like Family Guy is for you.
This is actually one of the last classic Family Guy episodes that I can think of. They put more effort and attention into this episode than usual, probably because of the opportunity they had to do this. The animation is also better than usual, and I think a lot of it has to do with Peter Shin's direction. He worked for The Simpsons back in the day, and he was able to integrate the Griffins into Springfield without having them look weird (like dimming their eyeballs and making their skin a little darker). The episode feels more like a movie than an episode half the time, but it doesn't become livelier until the Griffins come to Springfield.
I remember when this episode came out and everybody was worried about how the Simpsons would be portrayed and being protective of them. I could understand that if this crossover was made in the 1990s, but nobody should be trying to protect the Simpsons characters at this point. They lack any energy or integrity or unique qualities these days, so as long as Family Guy didn't do anything extreme, their portrayals would have been just fine. I didn't have any problems with their characters. I thought Homer was great in this episode, especially at the end where he talks about how important Duff is to his life. It felt like something he would say in the earlier seasons.
I also like how they went out of their way to highlight how different both shows are. They didn't try to write the Simpsons characters like Family Guy characters. When Stewie made that prank call, Bart didn't even know how to react. Lisa was legitimately disturbed when Meg told her about Peter giving her a gun to hide and later when she cut Lisa's name into her arm. Peter actually thought it was insane that Homer would strangle Bart. Marge looked down on Lois for not wearing a bra. I loved all of those moments because of how realistic they were. The characters didn't understand each other, and that's what made it funnier.
There are some things that keep the episode from being perfect. The first act is just a standard Family Guy episode. I know it sets up the plot and there are some good jokes, but things really don't pick up until the family gets to Springfield. Unlike Lisa, I feel like Bart doesn't do that much on his own. He's just around for Stewie to admire. I don't like the implication that Peter and Homer made a porno with the gas pumps. The chicken fight definitely goes on longer than it has to, and they could have given some of that time to something else. But at least they go out of their way to make it look interesting. And to this day, I never liked that last shot of Homer being crushed by the spaceship. It didn't look cartoonish enough, it was just this huge object apparently killing him.
But at the end of this day, this was still a really entertaining episode, and it ended up being one of the last truly memorable Family Guy episodes. I loved all the fourth wall jokes, the allegory of Duff and Pawtucket beer being both shows, and this last joke at Springfield Gorge was so damn stupid, it was hilarious: "You see, I'm a family guy." "I understand. I'm a The Simpsons." They went all out in making this crossover feel like a big event, and the Simpsons characters were funnier here than they are on their own show. 4/5
