How do you make your game more fun/engaging?

I give my sims likes, dislikes and preferences but I haven't noticed that they influence gameplay that much. I give traits and lot traits that sometimes help them, sometimes are a bit of hindrance. The sim working to be a chef won't necessarily have the foodie trait and the music lover doesn't have to play instruments. I like to develop my sim's story going from their environment, where they are located and asking myself how would they live and what job would they have. I like to keep things pretty realistic so there are no cow farms in penthouses in my game, nor every skill object present on the lot. They don't fish if there isn't a body of water near their lot, and canal fish is only for mounting. Sims living in apartments don't garden on their balconies. Sims living in Sulani don't grow holly and those in Glimmerbrook don't grow coconuts. I give them hobbies that fit with their lifestyle and interests, and often they earn money with their hobbies. They buy things they don't have, like a Halloween pumpkin, or fresh fish, or a new bathing suit, or use the library or an internet cafe if they don't have a computer. I fulfil whims, but not always, and sometimes a character's story gets influenced by something that happens in the game, like a sim who got yoga as a hobby because the game drafted him to be a yoga instructor at the spa. Holidays are always interesting as not all sims will be able to fulfill them all on their own lot so you need to plan and travel somewhere.

I used to just cheat money in and then get bored a few hours later - but then I started my first rags to riches playthrough and never looked back. A rags to riches with difficulty rules while also trying to collect all the collectibles makes for a fun experience that can have you playing for several weeks because of how engaging it is.

I actually looked up some challenges last night to try and get me more invested in the game. I'm not a super great story teller in my head so having some sort of goal or direction might help in holding my interest.

I'm not really into playing huge families or generations and I don't really play rotationally either so most of the popular challenges I've seen are things I know that I wouldn't really enjoy.

But the following list of ones did pique my interest and I will read up on them more:

https://fliphousechallenge.weebly.com/
https://onyeka001.wordpress.com/townie-life-challenge/
https://njadakaufey.tumblr.com/post/190113225737/witch-legacy-challenge-rules
https://forums.thesims.com/en_us/discussion/964395/a-free-will-experience-inspired-by-other-free-will-challenges
https://kateraed.tumblr.com/post/639063812678549504/whimsystories
https://aliennooboo.tumblr.com/post/647564479410962432/live-for-something-ts4-legacy-challenge-the
https://forums.thesims.com/en_US/discussion/974354/stranded-a-multi-household-rotation-survival-gameplay-challenge
https://illusorythrall.wordpress.com/home/challenge-rules/build-challenges/100-day-creativity-challenge-rules/

I don't play on console, so I hope you don't mind me popping in like this. To answer your question, I suggest you start with a Sim that you can invest yourself in. Make the Sim an interesting sort of character. I like to give two positive Traits to one weak Trait to help balance out a character. Figure out what you want this Sim to be and do and how their life should go and then play in that direction. Sometimes, the game will throw stuff at you and it's how your Sim reacts that makes it interesting. If the worst happens, remember you, the player, are in charge. Either roll back a save and try to prevent what happened or continue to play through the bad scenario to see what happens, next.

If I have to pick. I would just put in like traits and a storyline for my sims and when I make the storyline I sometimes just start a new save but I just wanna make it so that the storyline is interesting and on topic. I was trying to get my sim to complete her aspiration and then I just make new characters and it would be nice that I just get anything started and hopefully that the story goes well. But I really like how the game just engages you to play the game. I haven't played the Sims 4 for a long time and it just starts to want me play more, and I like the feel of that.

I just started playing Rags-To-Riches challenge. But my own rules. It took me a few tries to finally get to one that I really liked and I've stuck with this one for a while (which is saying something for me). But before I did any challenges, I just did the boring play which I don't know if I can go back to now. And I also added some mods (first time ever me too!) that add more challenges as well.

Sometimes I play as a premade family to add more adventure to the game.

I don't play on console, but you could look up some Sims 4 challenges for gameplay ideas. The scenarios are a good place to start, too. If I have to decide, though, I would make up a story for my Sims. You could share your story, or play out the story in your mind.

I agree with a few people in here who were mentioning looking up challenges, I've done that myself if I've ever gotten bored and wanted to spice things up a bit. Recently I made an evil sim who had a shed out back with a secret basement room where he would lock up his victims to be fed to his cowplant. I also made him try to lead a normal life otherwise -- he had a successful career as a detective and an unsuspecting wife and kids, and there was a specific "type" of sim he would scope out to be his next victim (blonde young adult females.) Of course a lot of the fun of it came from the story I had going on in my head. :) One challenge that I've been meaning to do next time I need a break from normal gameplay is the alien takeover challenge: https://forums.thesims.com/en_us/discussion/837731/the-sims-4-alien-takeover-challenge

I am very into generational/legacy type gameplay, personally. I get so attached to one sim family and I love playing around with their genetics and seeing how the next generation turns out, so generally I can go on like that for awhile and not get bored. One thing I try to challenge myself to do with each new heir to a generation is play with different traits/careers/skills/hobbies that I either haven't tried before or haven't used very often. Creating drama can be fun and interesting as well but I tend to end up feeling guilty lol. I also love building so if I get burnt out on gameplay sometimes I'll just go on a building spree for a bit.

I create lots of drama like an soap opera with aliens, vampires, witches and now werewolves, my sims cheat on each other all the time and I had a sim that used to woohoo elders to death and have grave stones in her back garden and host killer dinner parties with the pufferfish nigri dish