Haha what? You can't say silly things like that with out examples
Most weapons in IW's games are much more viable than in the other games. Snipers for instance featured the very best balance in the series with Ghosts, but for some reason neither Sledgehammer nor Treyarch have used these improvements in their own games; the latter has tried to tweak them in their own way for BOIII, but in the beta they still felt underpowered next to the usual weapons. And that's just the thing. In any non-IW COD, it's SMG/AR territory all day, every day. Little else is viable, ever. Ghosts not only had the most viable snipers and LMGs, but it even added the category for marksman rifles, which were quite fun to use and which neither Sledgehammer nor Treyarch have put into their games so far, inexplicably.
Still on the subject of weapons, I've always felt that in Treyarch's games most weapons within the same weapon category felt quite similar to each other. There's not enough difference when going from, say, one assault rifle to the next (unless it's a 3 round burst one or something). This is not the case in IW's games. The weapons are balanced to be more unique, and they indeed feel different enough when going from one to another, even within the same weapon category.
Then there's perk and class variety. I would have thought that after BO2's innovative pick 10 system, Treyarch and Sledgehammer would realize that it's a trivial and unnecessary limitation to take class points from the player for choosing, say, two perks of the same category (when perks are already assigned to their respective categories trivially to begin with). Ghosts' class and perk system wasn't innovative per se, I mean, it just took Treyarch's idea and lifted this trivial limitation. But as it stands today, with the lack of this limitation coupled with the biggest amount of perks seen in any COD to date (most of them being viable, mind you), it stands without a doubt as the deepest COD when it comes to class customization.
I already mentioned how Treyarch map design philosophy revolves way too much around CQB/SMG battles. IW may have had less than stellar map design with MW3 and Ghosts, but they always try to offer more variety with bigger maps, maps with a focus on sniping and so on.
Overall, when you put all of these factors together, there's little doubt that IW's multiplayers last much longer if you decide to stick with them, and that Treyarch's really don't offer very much at all after the first handful of hours. They may be really fun during that first stage, but after that there's very little to come back to.
