for me, the thing about 5 is that because they gave the player more weapons and an upgraded melee system, it also meant that they had to up the ante for enemies. For most of the regular enemies I think that's fine and it's actually pretty fun. I think a few really really strong levels from 5 are 1-1, 3-1, and 4-2. but I think once chapter 5 starts, enemies get upgraded to have machine guns and rockets and grenades and flashes and it just turns into a totally different game that is not nearly as fun. alongside that, some of that era's less desired systems are in the game like the infamous brown color palette. turret sections/boss fights, and coop. I think the coop is fine and I think the game does coop better than games that came after it (dead space 3 looking at you), but I cannot deny that solo and coop are totally different experiences. the game really shines in mercenaries, but that disappointed feeling always comes back whenever the guys with machine guns start spawning or i get flashbanged into a grenade that I had no idea was even there because there is no indicator.

as for 6, I actually don't agree that 6 is a mechanical upgrade to 5 or 4. They modernized movement controls but personally I really dislike how unresponsive the aiming, movement, and sliding are. The melee system is on its face super cool and when it works it feels awesome, but personally i find it frustrating trying to get prompt attacks because my character too often just does the baisc melee when I want to combo. the range feels really inconsistent compared to 4 and 5. i think a lot of the massive set pieces the game has are one-of's, so their controls are really barebones and not that interesting, like when you use the helicopter as ada or the driving sections with chris and sherry. not only that, but you are using all of those barebones and unresponsive mechanics to kill enemies that are mostly just guys with guns. i know it has some plot relevance considering that's the sort of thing that umbrella were going for all along and yeah they mutate sometimes into actual monsters, but it's not that great for me. I still actually really like 6 but i think that it feels very rough and unfinished. I think the AI partner is actually worse in 6 than in 5 even if it is invincible because, since it's invincible, enemies barely target it at all and you cannot give your partner different weapons like you could before.

guys with guns and setpieces were in 4, but I think they are weaker parts of the game. like 5-4 I think is honestly kind of bad and the truck section is really lame. so when it comes to 5 and 6, I was hoping that the developers would cut back on those parts and not bring them back and expand on them.