I just got 100% in Serious Sam: Next Encounter. I'v got to say I'm impressed, this is a full-fledged Serious Sam game with what feels like Zero corners cut due to it being on console, just the opposite actually, since there are some pretty cool features.
There is Alt Ammo types. Homing Rockets, Sonic Blast Rockets, Homing Chaingun ammo, Bouncy SMG Ammo, etc... The most novel of which being the rare Laughing Gas for the Flame Thrower, which is a guaranteed death to even the strongest enemies in the game.
Probably the best idea Next Encounter has is the Killing Spree, once you earn a 20 kill combo you enter Killing Spree mode which will double the points you get from kills, but best of all doubles the speed Sam Runs at. That Speed boost from performing well feels like it should be in every Serious Sam game, and getting high points actually has a Purpose since you can earn Gold medals at the end of levels which will unlock The Lost Levels, and Cheats.
Next Encounter also features 3 Vehicles, although surprisingly you'll only see one in the main campaign, The Jeep that fires homing rockets, it's fun to abuse the Homing Rockets, but you also need to make sure enemies don't destroy the Jeep. The driving controls might be the only flaw with the game, since they control unlike any game i'v played. It took me a while to realize these were RC Car Controls. Left Joystick is forward and reverse, Right Joystick is turning. You can get used to it, but they made the right call in Serious Sam 2 by just having the Halo Ghost rip off Hover Bike controls.
The other 2 Vehicles can only be found in the Lost Levels you unlock by earning enough Gold Medals. One would assume these were less polished levels they threw in as a bonus, but not at all. These levels are the exact same quality as the main campaigns, and they can be slotted in to the campaign neatly, Sam even has Unique Dialog in them. Maybe they though the campaign being 42 levels instead of 32 was a bit much, But as mentioned, Two entirely unique vehicles are found in the Lost Levels. The Combine Harvester which turns out was in Next Encounter first, and they re-used this idea in Serious Sam 4, and there is a whole level played in a Submarine equipped with double Mini-Guns and homing Rockets, Sam is shown entering the Sub in the main campaign, but you don't see it in action until this Lost Level.
Overall very much worth playing, and after all those years of me seeing the cover of this game in the Block Buster as a kid but never renting it, I've finally corrected that mistake.