People look at art for entertainment, primarily. The way I see it, there are probably... seven things that people want out of art. If it's going to get someone's attention, it should be...
- Sexy. So, porn, obviously. Sometimes non-porn of very attractive characters can work too. Think chesty girls in bikinis or other somewhat revealing outfits. Not really porn, but it works just the same.
- Funny. Memes, basically.
- Cute. Drawings of baby animals and stuff.
- Intriguing. Really weird, quirky, or otherwise unusual art sometimes gets popular for this reason.
- Trending. Fan art of whatever is currently the hottest topic in pop culture. Riding on the coattails of their success. If people are interested in a particular character, they'll like decent artwork featuring that character. The more popular the character, the more people will be interested. Hit it right at or just before the peak of their success for maximum effect.
- Offensive. Occasionally, you find some artists who get popular largely because they draw about controversial or offensive subjects, regardless of the other factors. It's harder to say that people actually "want" this one, but with how many people will deliberately seek such things out, they probably do want to feel enraged, at least subconsciously.
- Impressive. Absolutely stunning, god-tier artwork is always going to be popular, regardless of subject matter, but you have to truly be one of the best to do this.
So if you want your art to get attention, it probably has to hit one of these seven things. #7 only comes with skill and loads of practice, so that's not really something you can "choose" to do - you have to earn that one. And I'd avoid #6 because of all the negativity that comes along with it. So, for immediate results, the easiest options are going to be either porn or memes. That's why so many people get popular with those two (don't ignore how many artists get popular from drawing memes... it's a lot, likely even more than porn). There's a big audience for really cute artwork too - maybe not quite as big as the first two, but it's up there. #4 is an interesting path, though I don't see people pulling it off very often. You have to be able to come up with some really novel ideas to get anywhere with that, I think. It has to stand out from everything else out there, and there's a lot out there. #5 requires following the latest trends in pop culture, so it doesn't leave much room for drawing what you actually want to draw - unless whatever's currently hot in pop culture is what you really want to draw. If so, then go for it. However, it is an extremely oversaturated category, too. Lots of competition trying to ride the same wave.
Some of these combine, as well. For example, many of the most popular porn artists also have god-tier skill, such that their artwork is stunning to look at regardless of the pornographic content. That gives them a big edge over everyone else. Politically charged memes tend to make one group of people laugh and another group of people enraged, so they pull double duty in generating attention. Not all of it good, but still. Fan art gets a boost from pretty much any of the others.
There is also sort of an eighth factor when it comes to comics specifically. They have the advantage of carrying a narrative which single standalone images can't exactly do. So even with the other five factors lacking, you could have a popular comic just by having a good story. This, I'd argue, is the primary factor for comics. The others don't help as much, and you probably just can't get a comic off the ground if the story sucks. So if you want to go the comic route, that might be easier as that's really the only thing you need to worry about. Draw people in with a good story. No need to worry about any of the rest of it.
You can also just draw whatever you want. Draw what makes you happy, screw the numbers. If you really want attention, though, then just drawing whatever you want most likely isn't going to cut it. That's because it doesn't give people any of what they want. Look at those seven or eight things above and try to play into at least one of them. Now, full disclosure, I am primarily a porn artist myself - but I'm fortunate enough to actually really enjoy making it. I would honestly get bored making exclusively SFW art, and I'm admittedly not good enough in the other categories to get anywhere with them. Maybe I can pull off "cute" now and then, but; I'm not enough of a comedian to come up with memes, I don't have too many crazy unique ideas, my skill isn't nearly among the best of the best, and I usually don't care about whatever's currently popular. So, porn it is. But, surely, you can try to figure out something that you both enjoy drawing and that provides an audience with something of interest to them. Don't just draw, for example, SFW portraits or scenes of your OCs and expect that to get any traction. Draw something like that only because you personally want to draw it, and not because it'll be popular. Sometimes that alone is worth it.