Genealogy of the Holy War has long been well-regarded among Fire Emblem fans. It was the last game produced by industry legend Gunpei Yokoi, and thus regarded as his swan song. Technology had really caught up to the video-game visionaries of yesteryear, meaning FE4 would be the complete package and cutting edge in graphics, sound, and sheer size and scope of a game. The game featured gameplay innovations that were highly influential on the future of the series, perhaps most importantly the weapon triangle (Axes beat lances, lances beat swords, swords beat axes). But beyond its place in history, Genealogy of the Holy War is an exceptionally deep game on its own terms.
"Deep" is the best way I can describe FE4. It has a deep story, deep lore, deep mechanics, deep strategy. The game is demanding of your time and attention if you want to complete it. That's not to say that it's overly long. Time to complete is usually less than 40 hours, although this is longer than pretty much every other Fire Emblem game excepting #3 and #10. What I mean to say is that Genealogy of the Holy War has a lot of moving parts - many, many characters with unique skills, abilities, movement, etc.; mammoth maps with varied terrain and enemies; a tedious and bulky item and money management system; An elaborate and complex love- and second-generation system. On top of that, the game is not especially welcoming to newcomers. I beat the whole game without knowing the 'weapon triangle' even existed, and though I knew that progeny characters would be better than default characters in the second generation, I had no strategy in pairing or passing on weapons.
That being said, I'd recommend playing this game with a guidebook of some kind. There are online resources like fan-made wikis and video game walkthroughs, but this game has a plot twist that's really good, so you don't want that spoiled. A guidebook could help you pick up key items and recruit characters that you wouldn't have know about otherwise, and make plans for the second generation. Playing on an emulator with save states and a fast-forward button may also be helpful as you explore different routes and move more quickly through the game - the game does have its own built-in saves though if save states aren't your thing.
Genealogy of the Holy War is deep, so like I said, it may not be for all players. I struggle to give it a score out of 10 because I have very mixed experiences with it. At times it was slow or frustrating or the music was grating. After playing, I'm disappointed because it feels the game punished me for things I couldn't have known how to do properly because the game never told me about them. On the other hand, I thoroughly enjoyed the sprawling scope of this massive story. It really feels like playing a gargantuan continent-spanning decade-spanning epic holy war, though when you get to the end you realize you've played fewer than 40 hours. The translation kept an air of seriousness yet adventure, and the music and graphics haven't aged a day. Now that I've played and messed so many things up, I kind of want to go back and play the whole thing again and play it right! I rarely feel that about a game. I can easily recommend this game, though I know not everyone will like it. Some people just won't feel good about massive maps or constantly dying and having to reset the game or just the entire style or format of a game like this. Honestly, this game is like no other, and for that, I'd recommend you try it, because you just may love it.
Oh, and if you do enjoy grid-based and strategy-based JRPGs, there's a ton I can recommend from this era. Shining Force II for Genesis is really welcoming for newcomers. Shining Force III, Ogre Battle: March of the Black Queen, Tactics Ogre: Let us Cling Together, Bahamut Lagoon, Treasure Hunter G, Front Mission: Gun Hazard, Mystery of the Emblem, Super Famicom Wars; This era was definitely a good time for the genre.
