Is there a place where I can see what games were added to GOG catalogue at first, possibly in order and dated? Just curious. Maybe before I could have seen that on Magog (http://www.an-ovel.com/) but now it's no longer working.

The closest is likely the thread below, but it's also mixed with other GOG announcements:
https://www.gog.com/forum/general/gog_news_and_staff_threads_2008/

For the very first ones, you could check the earliest snapshots of the catalogue or search page.

I'd use MaGog's DB dump an-ovel.com/downloads/magog.txt and order by attribute "add_date_num".

Result for 2008:

add_date_num,title
20080722,1nsane
20080722,Conquest of the New World
20080722,"Descent 1+2 [removed on Dec 18, 2015]"
20080722,Descent: Freespace Battle Pack
20080722,Die By The Sword + Limb From Limb
20080722,Evolva
20080722,"F/A-18E Super Hornet [removed on Jan 11, 2018]"
20080722,"Fallout 2 Classic [Premium] [removed on Dec 31, 2013; data from Oct 12, 2013]"
20080722,"Fallout Classic [Premium] [removed on Dec 31, 2013; data from Oct 21, 2013]"
20080722,"Fallout Tactics Classic [Premium] [removed on Dec 31, 2013; Dec 27, 2013]"
20080722,Freespace 2
20080722,Giants: Citizen Kabuto
20080722,Invictus: In the Shadow of Olympus
20080722,Jagged Alliance 2: Unfinished Business
20080722,Lionheart: Legacy of the Crusader
20080722,M.A.X. + M.A.X. 2
20080722,MDK
20080722,MDK 2
20080722,Messiah
20080722,Sacrifice
20080722,Shogo: Mobile Armor Division
20080729,Descent 3 + Mercenary
20080729,Earthworm Jim 3D
20080729,Shattered Steel
20080807,"Original War Legacy Version [removed on Jun 22, 2014]"
20080908,Kingpin: Life of Crime
20080909,Hostile Waters: Antaeus Rising
20080909,Perimeter
20080916,Redneck Rampage Collection
20080916,Stonekeep
20080923,I.G.I. 2: Covert Strike
20080925,Soldiers: Heroes of World War II
20080930,Kingdom: The Far Reaches
20080930,"TOCA Race Driver 3 [removed on May 29, 2009; data from Mar 30, 2009]"
20081007,Earthworm Jim 1+2: The Whole Can 'O Worms
20081007,"Second Sight [removed on Sep 26, 2012; data from May 4, 2012]"
20081014,Battle Chess Special Edition
20081014,"Colin McRae Rally 2005 [removed on Jul 29, 2009; data from Dec 19, 2008]"
20081021,Operation Flashpoint GOTY
20081022,Castles 1+2
20081028,Disciples: Sacred Lands Gold
20081028,Gothic
20081104,Ghost Master
20081104,Jagged Alliance
20081104,Sensible Soccer 2006
20081111,Jagged Alliance: Deadly Games
20081111,Sacred Gold
20081118,Unreal Gold
20081118,Unreal Tournament GOTY
20081125,FlatOut
20081125,Unreal 2: The Awakening Special Edition
20081125,Unreal Tournament 2004 Editor's Choice Edition
20081202,Disciples 2 Gold
20081202,Jagged Alliance 2
20081204,Arx Fatalis
20081209,Port Royale 2
20081209,"Simon the Sorcerer [removed on Apr 3, 2018]"
20081211,"Simon the Sorcerer 2 [removed on Apr 3, 2018]"
20081216,Oddworld: Abe's Oddysee
20081217,Darkstar One
20081218,Beneath a Steel Sky
20081218,Lure of the Temptress
20081223,Oddworld: Abe's Exoddus
20081223,Patrician 3
20081230,Broken Sword 2: Remastered
20081230,"Feeble Files, The"


EDIT
Added Operation Flashpoint GOTY to result list. Removed from GOG catalog 'round 2009-01-20, later re-released as ARMA: Cold War Assault.

Thanks y'all. This was what I was looking for, very interesting!