Where are the older titles from the series? Part 2? Part 3? HD Remasters from Parts 1?

No buy, before those are released here CroTeam. Just as with Part 4 before. Sorry.

Would be nice to see Croteam release the earlier Serious Sam games here for completeness sake.

I'd like to be able to purchase Serious Sam 2 and 3 here. (granted I'd only get them on sale)

Well THIS was an unexpected but very pleasant surprise!

Technical issues aside, SS4 had the best weapon and enemy balance of the series. Total CPU hog, though.

Hopefully this version will be a little more stable. Maybe a patch for the base game too?

A stand-alone expansion? Very nice.
The part in Russia indeed felt very short. Hopefully, this will be as good as Jewel of the Nile was for Serious Sam 3 (which I still hope eventually shows up here).

Wasn't expecting 5 levels, which is a very nice surprise.

why? since ss4 was on gog at release, and you know that, the real surprise would be if now this ep would not be released here too. (your comment would make more actual sense if ss4 did not release on gog)

same as, i assume, as another "same" example, the new squarepants bob will be releases here too. if it doesn't release on gog, then, to me, that will be the "unpleasant" surprise. i assume based because thq seems good about gog releases (bless them, for now?) the new one will be here day one or pre order even.

store .steampowered .com/app/1282150/SpongeBob_SquarePants_The_Cosmic_Shake/

as for 10% off, that's fine, however steam also has a pack bundle discount bringing the game to $15 (instead of $18) if you also have serious sam 4. so a little peeved the same doesn't also apply here on gog, for i have ss4 (deluxe to boot).

store .steampowered .com/bundle/24406/Serious_Savings/

whilst that extra $3 means squat to me, i will (for now) not grab this pack, out of anger. the steam pack discount doesn't also require any of the other games that are not here on gog, so gog (croteam!!!) could/should also have the same pack discount too. you know, loyalty discount. business is business.

A pleasant surprise because I didn't know an expansion was coming out.

I thought SS4 was abandoned in favor of Talos 2.

edit: but yes, a discount for ss4 owners on GOG would be nice, yes.

I didn´t know that this expansion existed. Insta-wishlisted!

Was an instant purchase here. Perfect timing on my end! :D

This looks great! Can we get Serious Sam 2 and Serious Sam 3 too? Please? Pretty pretty please?

Isnt Serious sam 2 already here?
Serious Sam: The Second Encounter
https://www.gog.com/game/serious_sam_the_second_encounter

Or perhaps im getting confused by names of the titles?

Haha, that's a very common misconception. Serious Sam 2 is a different game from 2005. :)

Serious Sam: The First Encounter and Serious Sam: The Second Encounter together are Serious Sam 1.

A prime example of what would have been an immediate buy for me. Unfortunately years on, not even so much as acknowledgement of any issues has forced me to not buy. SS$ was one example where offline installers do not have all the patches, and the compressed archive is huge and unoptimsed:
https://www.gog.com/forum/general/provide_a_full_and_complete_changelogged_download_system

Unfortunately the only "progress" on the site now seems to remove things, support, product descriptions at launch etc.