So here is my first train to celebrate such accomplisment :D (6 games, lvl1+).

ETD: 19:00 UTC 05/05

EDIT: This is in the Puzzles category for a reason :D

EDIT 2: A subtle hint. Do you know how this is called?

EDIT 3: One day remaining and still too few entries for #6. A new hint that should help you get there when used together with the previous hint: One of these "fun (?) facts" is not like the others.

EDIT 4: Remember to put the / at the end.

Solution:

Read the years of each fact as ASCII codes: 48 => 0, 79 => O, 82 => R, 67 => C, 74 => J.
Every GA started with "fun (?) fact", except for the fourth one that said "FUN (?) FACT", so the fourth character is the only one uppercased. 0ORCJ => 0orCj.
Finally, put together the GA link: http://www.steamgifts.com/giveaway/0orCj/.