As of last night my wife and I (I will now say "we") officially finished the Kingdom Hearts series! This is a huge accomplishment for us, and one we've been working on together for the past three year as we awaited the launch of Kingdom Hearts 3.
If you're uninitiated, the first game originally came out in 2002 for the Playstation 2. The series has since expanded with games releasing on the DS, 3DS, PS3, and PS4. Since their original launches, all of the games are now available in some form or another on the PS4, contained with the Kingdom Hearts HD 1.5 + 2.5 ReMIX and Kingdom Hearts HD 2.8 Final Chapter Prologue. (Links are to the official KH website)
The Order to Play Kingdom Hearts Games
The order we recommend for playing the Kingdom Hearts games is as follows, and this is the order we'll share our thoughts. Note that this is not the chronological order, but rather the order we feel the series presents itself best in, and the order where everything will make most sense -- if that's possible.