Is it your first bike? If so, the best one is one that you'll get a lot of hours riding, and usually that means a secondhand Japanese model. Ninjas are a meme for a good reason, they go fast and last a long time and don't do anything that they don't need to. Their equivalents from other companies, the GSX-R and the CBR, are basically exactly the same bike, just pick the size you're comfortable with and go for it (my first bike was a 750 so don't start on a liter bike but also don't feel like you need to start on a 250).

I would also recommend looking at Royal Enfield if top speed isn't as important for you - they're the best value for money in the industry and it isn't even close, but they primarily target the Indian market which has fewer highways so their bikes are slower, but are more useable in less than ideal road conditions. I think RE is still doing the 3 year warranty thing too, which is more than anybody else does because they're trying to shake off their reputation for making shitboxes (which wasn't entirely undeserved, but it's a new era now).

Just be sure to keep an eye on your used market for a while before making up your mind, you'll get a sense of what's a deal and what's overpriced, and don't buy it unless you can test ride it first.