The M16A3 is probably the best all-around assault rifle in the game at the moment. Mainly due to the M320 LVG + HE. You can get an insane number of kills with its multiple UBGLs and the gun itself is very consistent in close-mid range with a high ROF and good mag capacity. The only weakness imo is lack of the NATO red dot/holo for whatever reason, it has the Kobra instead which seems like an oversight (I'm not a fan of the reticle on it personally). It would be the perfect gun if it had the Ghost Hybrid. The RM68 is equally as good in close-mid, but it lacks a second UBGL and has low mag capacity.
The M416 is also an honorable mention with the M16A3 since they are basically the same gun, but the 416 lacks the Champion muzzle brake for some reason and has a lower ROF which makes it feel much worse to use for me personally.
The SFAR and G36c (I'm not calling it the "GEW", lmao) are better for mid-long range, but the lack of UBGLs holds back the G36c a lot unfortunately. SFAR is the same as always, 4 body hit kills or 1 head 2 body with high mag capacity with the drum on top of being high-power ammo and a * load of UBGL options, has the Ghost Hybrid optic making it perfect for any situation, and is very manageable recoil-wise. Biggest issue is the slow reload speed using the drum mag.
For close-close range, I will tell you a secret: the M5A3 with close combat mags and short barrel. It has 910 ROF with 45 firepower, plus two UBGL options, and a 40 rounder standard mag to swap if you run out of close combat. It has every good optic available as well. It has the STNR laser and BCG grip for whatever close range flavor you prefer if you don't want to use the UBGLs. It's honestly wild how good this gun is at close range. It has SMG rate of fire with AR firepower and range. It's better than every actual SMG and even the "SMG config" BSV-M. The only reason to even use an SMG over it is for mag capacity, imo, but even then, why? You could have an SMG equivalent with higher firepower and UBGLs. The MTAR also used to be this good and essentially was the same thing, 50 firepower with 900 ROF, but sadly it was nerfed and lacks the attachment selection the M5A3 has. MTAR is still a quite good option for exclusively close range though.
Mentions in some non-assault rifle categories: MP9 and PP-29 still quite good as always, Avancys and RPK-74M are both obscene in their class, DM7 and BSV-M for DMRs (BSV is one of the most versatile guns in the game for mid-long range as well), DXR-1 and the new XCE Bar has actually probably pushed out of the GOL Magnum for me on snipers, BFP .50 might as well be a primary weapon because it one shot kills with headshots at close range and is even extremely effective at mid-long range, you can unironically countersnipe with it.