Please tell me which Final Fantasy games are actually worth playing, fellow weebs
The original Final Fantasy (1987) was a competent D&D-clone with influences from Wizardry and Ultima III, though there are better, similar games you could play starting with those two.
Of the next four games in the series, three were originally released only in Japan. Although they eventually had international releases on later systems (i.e. the Sony Playstation), I've never played them and so can't really comment on FFs II, III, and V.
Final Fantasy IV (1991) was originally called FF II when it was released outside Japan on the SNES. It's the first game from the series in the JRPG subgenre, having a heavy focus on story and characterization, and taking advantage of its excellent graphics and soundtrack; thus setting the standard for later games in the series (at least through FF X in 2001). It also introduced the Active Time Battle system, which would be used until FF X reverted to a turn-based system.
Final Fantasy VI (1994), which was originally called FF III in its SNES release outside Japan, is similar to FF IV but has a better soundtrack (IMO the best in all videogames, despite the limitations of the SNES' sound capabilities), inspired steampunk setting, and ensemble cast of player-characters. Definitely the best of the series.
Final Fantasy VII (1997) was a disappointment. Even in the realm of graphics, although it made a technical leap to 3D graphics on the Playstation, these were crudely done, especially for characters, and it's the only FF that looks ugly --- even before taking into account the inevitable aging of 3D graphics. The narrative and characters were intentionally 'darker and edgier', with an angsty teenage vibe. Combat was reduced to just 3 PCs at a time.
Final Fantasy VIII (1999) was likewise disappointing. Although it managed to improve the graphics considerably, combat became even worse, with an irritating junction system, the necessity of 'drawing' magic from enemies and stocking up 300 of each spell, and prolonged 'guardian force' animations. The plot was generally better than the previous game but fell down hard at the end, and the player-characters were non-entities with an age range of 15-19.
Final Fantasy IX (2000) intentionally harked back to earlier games in the series, especially FF IV, and therefore managed to be better than the previous two games. Graphics adopted cartoonish designs that might be off-putting at first but actually suit it. Combat returned to 4 PCs at a time.
Final Fantasy X (2001) jumped to the Playstation 2, with graphics that were amazing at the time, though subject to the aging that afflicts all 3D graphics. The ATB system was replaced with a turn-based system operating at the individual level, letting the player know which characters/enemies had the next few turns in advance. Although only 3 PCs were available in combat a time, you could switch PCs in and out of combat without losing a turn. Exploration, on the other hand, became even more linear than in earlier games. The setting was a rather unique, post-post-apocalyptic environment. This was the first game in the series to adopt voice-acting, with unfortunate repercussions. Nobuo Uematsu only composed part of the soundtrack (more or less all the better tracks) and parted ways with the series soon afterward.
FFs XI and XIV were MMORPGs.
Final Fantasy XII (2006) had issues in development, with the director resigning. What emerged was heavily influenced by MMORPGs. Combat was based around a 'gambit' system where the PCs (3 at a time) fought automatically in combat according to a series of simply if-then statements, and the player mostly just sat back and watched, with occasional interventions. The second half of the game was twice as long as it should have been, i.e. actually two-thirds of the game rather than half, with remarkably little occurring in terms of plot development or characterization. Of the 6 PCs, half shouldn't even be in the game, especially the character who serves as the initial protagonist.
Final Fantasy XIII (2009) had even more serious issues in development before its ultimate release on the PS3. The game was so 'streamlined' that you spend the entire time effectively running down a tunnel, without even a pretense of exploration. Combat consists of watching the PCs (3 at a time) act according to whatever role (of 6) they've been assigned, with the player occasionally shifting from one set of roles to a different one. The tutorial lasts into the second half of the game, before you are finally granted access to all 6 roles for all 6 PCs. Similarly, the plot and setting are a mess, and all 3 male PCs are annoyingly whiny. If FF XIII count as an RPG, it's the worst RPG I've ever completed.
Final Fantasy XV (2016) made XII and XIII seem like pikers when it comes to troubled development. It was originally intended as a tie-in to FF XIII and underwent numerous wholesale transformations before its final release on the PS4 as an open-world road-trip RPG. In many ways, the game seems influenced by Dragon's Dogma, except far worse in every important respect. You're stuck with just 4 PCs, there's almost no character development or customization, combat consists largely of holding down a button, and even the exploration mostly involves driving your car as near as possible to your destination and then running a brief distance to reach a combat (there are eventually a few, small dungeons). The plot is a complete mess from very early in the game, and there comes a point where you leave the main landmass and the game becomes almost completely linear until the end.
tl;dr FFs VI, IV, and IX; and possibly the original