I'd say the Black Ops series is my favorite, with BOII being my favorite of the bunch. It has a good balance between the contemporary and futuristic weaponry. It doesn't go too far like Infinite Warfare, but it's not as archaic as the WWII games, which are okay.

Black Ops series

Black Ops is the most consistent. the original is the best one to me.

MW1: Great start for the series. Prefer the campaign as the multiplayer doesn't hold up as well as others.

World at War: Fun co-op campaign and good(ish) multiplayer but there are better entries in regards to both.

MW2: Excellent campaign and fun (but frustrating) multiplayer where every gun/perk feels overpowered.

Black Ops 1: Best balance between all three game modes (Campaign, Mulitplayer, Zombies). Probably my overall favorite.

MW3: The most underwhelming entry in the series. None of it's modes shine in comparison to prior and later entries.

Black Ops 2: The campaign had ambition but ultimately I don't particularly care for it. Multiplayer meanwhile is the best in the entire series.

Ghosts: I really, really, really, really, really, do not care for this entry. There are too many problems to list.

Advanced Warfare: I really liked this one, both campaign and multiplayer. Granted, I thought it had the better jetpack movement system. Zombies was fun but wish it had been included for free and not dlc exclusive.

Black Ops 3: Worst campaign imo. Meh multiplayer. Can't even remember what zombies was like. Played the game for a month after launch then forgot about it.

WW2: Token campaign. Fun but flawed multiplayer (it got better but that took some time). Same story as BO3 with zombies.

Black Ops 1 and 2 had both fun multiplayer and zombies so they win.

Black ops

Modern warfare. All about cod4 and mw2 for me

It's a mix up between MW1-2 and WaW.

Agreed. Although if COD4 released today, it wouldn't be very successful in my opinion.

World at War isn't part of the Black Ops series, it's actually set in WWII.

That out of the way, Modern Warfare.