Broken Base: After SOCOM 2, which the fanbase collectively agrees was best SOCOM game, with the original not far behind in quality, the fanbase splintered in many different directions with the following titles (see Contested Sequel).
Contested Sequel - Averted with SOCOM 2, which received as good or better a reception as SOCOM 1, but the other sequels are more polarizing:
SOCOM 3 (and by extension, Combined Assault) - To multiplayer, Zipper added the ability to swim and modify your weapons, a day/night cycle, vehicles, optional spawn points, and created bigger levels to provide 32-player matches. Fans either embraced the features as welcome additions to the SOCOM franchise or rejected them as a poor man's Battlefield. With the single player, however, SOCOM 3 is widely considered the best one.
SOCOM Confrontation - An outside developer (Slant Six) basically created a "greatest hits" version of the SOCOM multiplayer, much like how SOCOM: Combined Assault did for the PS2 games. Same lobby system, same modes, same weapons, same everything, alongside some new maps. It's either hailed as a nice throwback to the series, or ridiculed for its antiquated look and gameplay. Lack of campaign mode was a downer for some. Some have blamed it for the death of the franchise, as it's multiplayer had problems for weeks after launch, making getting into games difficult, which some believed soured people on the franchise to the point where they had no urge to pick up the fourth game.
SOCOM 4 - Zipper finally released a proper sequel to SOCOM 3 onto the PS3 six years after SOCOM 3, though many of the single-player and multiplayer features were altered, alongside the general gunplay and controls. The old multiplayer lobby system was replaced by a matchmaking one, the older non-deathmatch modes were replaced by newer ones, and respawn settings (though still optional) were emphasized more compared to the older games, and campaign mode became more action-movie oriented than methodical and tactical. The fans who don't like the game loathe it for these reasons. The fans who do accept SOCOM 4 generally enjoy it, though with some reluctance because of its questionable design.