"Best" is a very relative thing. What's best for me is probably not best for you.
With that said, a general concept of "best" would likely require:
Function- Luminous face that is easy to read and attached to a reliable and accurate movement that easily conveys all the information the wearer desires at a glance. Water resistance sufficient for moderate use in/around water.
Quality- Overall standard of design and construction at least above average compared to similarly priced competition, preferably offering features that are rare at the price point.
Style- This one is more subjective than the others, but if you are looking for a single "best watch" then styling should probably be fairly conservative and equally at home with dress clothes and casual stuff. Individual taste is the most important factor in this, but most would probably agree that a massive digital plastic thing doesn't look too hot with a suit.
Also, I don't like quartz wathces, so everything I recommend is going to be mechanical. Something made in-house gets my vote over a similar item with an everyday ETA movement, as well.
Under $200
Selection is pretty small here.
I vote Seiko Automatic w/ 7S26 movement. Price varies widely, but $150 is a good average. The 7S26 is a great little piece of engineering, not fancy or pretty but dead reliable and capable of good accuracy once it selles in. Case and band quality is comparable to other Seiko products, which means quite good. Nobody will confuse them with an Omega, but the quality is respectable.
These come in a variety of case styles, some of which are rather cartoonish. There are others that have more of an understated look that works a whole lot better. Unlike other low-priced mechanicals (Sandoz and Invica, for example) the Seikos are unique don't look like simple Rolex clones.
Under $300 and Under $400
No question in my mind, #1 with a bullet in this price range is the Poljot 3133 chronograph series. It is (in my opinion) almost obscenely superior to anything even remotely near this price range.
The quality of these watches is fantastic, in my experience they can stand shoulder to shoulder with recent production Omega and Rolex and give up nothing in terms of fit and finish. Screwed crown, water resistant pushers, rotating bezel that is smooth like glass, and screw down diplay back raise the feature content into another level as well. I once had a watch dealer offer to buy mine (unsolicited) off my wrist for several times more than they actually cost.
The 3133 movement is reliable and accurate, and has actually been proposed as the next source of movements for the Swiss watch industry since ETA announced that they will start limiting their production. Accuracy is generally good, and chronometric performance is possible if the watch is well adjusted. Nice looking movement, as well.
There are literally dozens of styles available with this movement, from very traditional pilot's watches to high polish dress watches to modern sports watches. Not very many divers, but a few. If you are one of the Ti fans out there you can get that, too. There is almost certainly a 3133 that will fit your personal style. I like the Cosmos myself.
Many watch manufacturers like to bang the drum about having some connection with aviation history or being the "choice of professional pilots/elite commandos/James Bond" or some similar copy. Most of it is trash, but in Poljot's case it is true. They were the first watch in space (Yuri Gagarin wore a Poljot Sturmanskie) and for the Soviet years were the issue watches for the Russian military.
The only drawback is that the 3133 is a hand wound movement, but this is a minor one compared to all the advantages that the product offers. I actually prefer it, and won't wear an auto if I have a hand wind available.
You can get a mechanical chronograph with quality that easily rivals an Omega for under three hundred dollars. If there is any other watch that offers such a screaming value I haven't seen it.