Question looks simple, what are the best openings as Black?
When I was playing OTB as a junior, being a proud "child of informator", I wanted to win as Black, who doesn't?
Having lots of time to study openings, I chose the best based on what I was seeing the best chose as Black. Back then my view was that best equals Fischer and Kasparov so I played the Najdorf and the King's indian. Later on I added the Benko and the Sicilian Dragon (after Kasparov employed the Soltis variation vs Anand).
I read allot about these openings, was lucky enough to have a well known coach, second of a very well known GM, who was also providing me analyses.
This tactic payed off several times, probably the most happy moments were some miniatures versus a couple of FMs, while being below FM level myself.
Chess was taking too much time however and I had to quit it, after all I had to prepare for Uni instead of preparing for tournaments.
Having stopped playing OTB and not having a clue about internet chess (if it was there in the 90s) my main involvement in chess was playing against some friends from the club (from expert to FM level), started reading "real chess" literature, instead of memorizing Dragon-Yugoslav-Soltis move 27, I read Nimzowitsch, endgames, Dvoretsky and studied games by world champions.
After reading all that I realized one thing, I never knew anything about chess, I just was good at tactics, like most junior players, and could calculate good enough to get a win after a won position in the opening.
Then work+later uni years didn't allow me to play chess but last year I started playing again online. I still have my old notebooks but most of the analysis is now irrelevant, mainly because "fashionable" lines change as time passes.
If playing chess again was to bring decent results, I had to choose a Black repertoire taking in mind that now I can't sit in my room studying chess all day seven days per week like I used to, I live abroad and therefore the magnificent trainer I had cannot train me atm, my dad will no longer be paying for 4 new chess books per month (bit too old for those "dad stipends") so playing razor sharp lines was out of the question.
Another factor is that long breaks from chess cause big hits in ability to calculate, endgame knowledge, position evaluation etc, (oddly they do not affect planning!), so I had to (and still do) spend time on revision of Dvoretsky, endgames etc.
Lastly, I am not happy anymore to beat an opponent because I memorized something, being creative sounds more fun for a hobby!
This led to new "best" openings, that I can afford to learn and hopefully one day master. These are the Caro-Kann and Queen's Gambit Declined. They have allot to teach me about chess and I have allot to learn from trying to grind equality rather than just relying on wild tactics.
Sure they provide very little, if any at all, chances to win as Black but if this was good enough for great masters like Capablance, Karpov and Petrosian, who am I to argue if these openings can be the "best"?
The only downside is that it takes time to learn these new openings, after 3 months of playing them almost exclusivelly, I still feel that home is Najdorf/King's indian and I'm making mistakes in my new repertoire. Like any "house move" I guess this one as well takes time before I can consider the new positions which arise on board as "home".