Alright, how do you define "better"? That's kind of a trick question: you don't. If you did, there would be no point in arguing, in polling, in giving prizes like the Spiel (or, you know, the Oscars), in making a top 100 games of all time list. The moment you define - as in, mathematical definition - "better" is the point where you leave the realm of speculative internet discussion and enter the realm of certainty.
Nobody actually wants to do that. Or rather, everybody wants to do that for things like airplanes' flight, rocket science, bridge construction et cetera. Things with actual consequences, things that may kill you if done wrong. But that quickly becomes academic and boring, so to keep it interesting, nobody actually wants to measure the worth of a game.
[I'm ignoring the fact that it'd be difficult to do, because as a race, humans have measured a lot of difficult things arbitrarily, when needed. How many years you need to spend in prison for a given crime? Isn't that arbitrary? Isn't that difficult to decide? We do it nonetheless, because it actually matters.]
However all those prizes, all those discussions, all those top 100 lists? They have to come from somewhere. You need to have self-imposed parameters for them. In the case of BGG rankings, it's a statistical representation of the tastes of a certain category of people. In the case of Tom Vasel's top 100 games of all time, the measure is Tom Vasel.
So let's talk about the BGG ranking system. It's biased: people that actually vote on BGG are already hardcore gamers. I'm pretty sure that Splendor would have more than double the votes of Twilight Struggle if that wasn't the case. Nonetheless, Caverna beats Agricola there. That means that, on average, even the part of the market that is invested enough to vote on BGG is partial to Caverna. That speaks volumes of how Caverna vs Agricola would pan out on a greater audience (if I had to speculate, Caverna would be received pretty badly, and Agricola would be totally hated, but that's speculation on my side). Does that mean Caverna is a better game than Agricola? Define "better".
It almost certainly means that Agricola is less generally pleasant than Caverna. It probably means that (given enough time) Caverna will sell better than Agricola. It probably means more people will play Caverna than Agricola in the future (given access to both, Agricola has had quite a lot of time to spread out that Caverna hasn't had yet).
I will say that, if Caverna and Agricola were put on the market at the same time, the following would probably be true:
more people would like Caverna than Agricola
very few people who like Agricola would dislike Caverna
a lot of people, including people who like Caverna, would totally hate Agricola
Caverna would sell better
Agricola would probably be quickly forgotten since its theme and mechanics are so similar to the more popular Caverna
Does that make it the better game? Again, define better. Does making more people happy make it a better game? Do you average relative happiness or only take the preferred game for everyone? (In both cases I think Caverna would win). Does having a wider audience, thus being able to be played more and more often, make it the better game? Does nostalgia, or simply being a precursor, play a role at all in the consideration?
In the end, you can probably rationalize the fact that Agricola is the better game. You may just value the opinion of a subset of gamers (those that like Agricola better). You may just take into account your own opinion and not care about that of others, or the opinion of the market. You can also try to scrape together something along the lines of "Agricola is better because it's tighter" or "because it challenges the player more" or "because it's harder" or "because it is more flavorful" (although you should probably notice that most of those words also lack an actual meaning, and are undefined, since otherwise you would have no discussions). But all that is largely irrelevant, because really. What does better mean? It's just an excuse to have pointless arguments over the internet.