Story-wise even 1 and 3 do not meet, no matter how the creators tried to make us believe that. In DMC1 it's stated right at the beginning that Dante lost both his mother AND his brother 20 years ago. And when Dante sees Nelo Angelo without the helmet it still doesn't ring a bell - and let's be fair, Nelo's face is less weird than the corrupted Vergil's but STILL recognizable to those who've seen DMC3 Vergil. Even when he gets the hint after receiving Vergil's amulet, the only memory that comes to him of Vergil is one when they were both little kids.
As for the places. In 1 you traveled between a castle, a ship, a town, underwater, the underworld etc. In DMC3 all the missions are in this damned tower. Even the underworld is still the tower somehow. And Dante's shop and a club do not count as extra places.
Don't get me wrong DMC3 IS awesome, but for me the places were pretty boring. I never felt any gothic atmosphere (the 2nd game had more than the 3rd) neither was I let's say "afraid" of any enemy. In DMC1 the enemies weren't "cheap" like DMC3 (examples: Bloodgoyles multiply if you hit them with the sword so you only need guns, the other guy with the huge shield in front of him who can only lose if you go hit him from behind, the annoying flying things that are ethereal and invisible when you look at them and should turn your back and shoot immediately if you want to hit them), they were just STRONG. You could hit them with all your might and they would COUNTER-ATTACK! Awesome. In DMC3 if an enemy is blocking you, you just keep hitting him until you break his guard.
You, my friend, have made a terrible mistake. And now, I will never stop talking. Ever.
I admit the story doesn't match up exactly. But, eh, that doesn't bother me all that much. None of those details really make much difference in the long run, and they have nothing on the plothole of Nero's existence. As long as you squint a bit, it's possible to see how the two connect. Which... isn't good, but I'm used to much, much worse.
As for the settings... DMC1 had a town?! Where?! I'll give you castle, ship, underwater caves, but
town? (Now, DMC2...)
Temen-ni-gru might have been just one tower (plus, beginning stage was town), but it was huge. The various levels were all pretty different, and we got a giant monster's belly instead of a ship. And I dunno about you, but I don't think taking out inexplicable gameplay shift swimming sections was a weakness. (I hate underwater stages.)
That aside, I don't think it's the settings themselves that are similar, but rather the general atmosphere. Dark, lots of ominous stone structures, gradually building evil presence that corrupts the atmosphere and increasingly trippy design toward the end.
4 - well, it's pretty sunny and you get to run around a tropical-ish forest. Lots of white too. (I know that might seem petty, but we
are talking about visual impressions...)
Gothic... well, I think it's a cool word. I honestly don't think you're supposed to be scared of anything in DMC. Like in Castlevania. You can whip anything to death. You can whip Death to death.
And didn't DMC1 have those Shadow things, the kitty-cat ones that were immune to swords? And I think in 3, there are enemies you have to attack in specific ways or they don't take damage (Durandal...?)......? But gameplay is a whole other thing in any case.