The reason no-one is saying, "Yes, go to Space Station X, fill your hold with Commodity Y and take it and sell it to Space Station Z", is because the trade system is dynamic and responds to the collective activity of players. A trade route remains super-profitable only if very few CMDRs are flying that route. Posting a "good trade route" on the forum is a surefire way to kill that trade route within a day or two. Most people who are maxi-trading their way to profits in the game don't want any competition on their routes.
So instead of offering specific routes, we can offer some general observations, and let you cruise about (or use EDDB/Inara/etc) to find routes that might fit those circumstances.
The most profitable non-illicit buy-sell commodity in the game is "medical diagnostic equipment". It is made in High-Tech economies and demanded by Service economies. So look for High-Tech economies in Bust, or stations where few traders are visiting, for the cheapest price (it can get down to around 1000 cr/t, but you're more likely to have to pay 2000 cr/t or so). Now fly it to a Service system in Boom; historically, I've found Sol and Alioth systems to be good, as there's lots of Service stations in these places and at least one of the station-controlling factions is likely to be in Boom at any one time, but find your own destination that works for you. A good price is anything over 5000 cr/t, though if you're real lucky or persistent, you can find some poor suckers (usually at a surface starport on a remote moon) prepared to pay up to 7000 cr/t. That's 3000-6000 cr/t profit.
Precious metals are also pretty good deals, if good MDE routes are proving elusive. Platinum is somewhat over-done and profits on platinum tend not to be as good lately as for gold and silver. Again, find mining and refining installations that are small, out of the way and rarely visited; they might have an abundance of precious metals going cheap. They're also in demand in lots of places; everywhere except Agriculturals, in fact. So find a nearby Boom state and cash in your rocks; making 1000-2000 cr/t should be easy, you might even make more.
For the humanitarians amongst you, "Outbreak" systems are a great source of credits as they pay extra-high for Basic Medicines; you can by these from numerous sources super-cheap (say around 300 cr/t) and sell them at Outbreak systems for 3000 cr/t. "Famine" systems likewise can pay super-high prices for basic foodstuffs, though I don't think they're as profitable as Outbreaks.
"Illicit" commodities - slaves, drugs, weapons and such like - can also be quite lucrative even when traded on the legal market in systems where those goods are not illegal, but finding profitable routes is less "logical", less "consistent" - and of course if your route happens to pass through systems where such goods are illegal, you better have your scan-avoidance mojo working well for you.
Whenever you find a really good trade route, remember two things: (1) don't tell anybody, until and unless you've finished with trading for the time being, and (2) even if you're the only trader running the route, you will eventually kill the goose that lays those golden eggs, and/or the circumstances creating the super-high profits (such as Boom, Famine or Outbreak states) will be resolved and change.