They're my favorite games. You'll appreciate 3 and NV more if you play them first however. Fallout 4 has some quality of life changes that make it hard to go back to the previous two, so I would suggest playing them first since they're still perfectly fine games. The DLC is also great for both games, as far as DLC goes in general.
If you wanna know about fallout 4 specifically though, it's a good game. It's not everyone hyped it up to be, but it does everything the last games did, while also adding in a Minecraft style building aspect to the game. You never actually have to do any of the building stuff though, save for a few objectives here and there in quests which aren't that troubling. The game play is great, voice acting is a nice change of pace for the main character, the world is interesting and fun, plus if you get it on console, you gave access to mods on there which is a first for console gaming. Its DLC is much weaker compared to the previous entries, but still interesting. I bought the season pass when it was 20 bucks, so it didn't really make me angry, but spending the money you would to get all of the DLC now would probably piss you off, so keep that in mind. Still worth it, but it's a headache and low on compelling story.
If you like skyrim or other open world games where you just make a character and go, you'll enjoy the fallout series. If you like shooting and retro futuristic themes and settings, you'll like fallout. Just depends on what your preferences are. And, just like any Bethesda game, bugs will happen. It's not so bad though, so that's good. I've had more bugs while playing with mods on my Xbox than I ever did when playing just the vanilla base game. The game also never crashed before I modded it, so that's saying something about the quality of the game's design. Usually vanilla Bethesda games crash at least a handful of times, but fallout 4 is pretty smooth. You most likely won't have any trouble with 3 and New Vegas either, but they are older and a little less polished. Note on NV, it was developed by Obsidian and they're known for bugs themselves, but they make a damn good fallout game, believe me. NV is almost better than 3, but that's a point of debate for later.
Anyways, enjoy the games if you do buy/play them eventually. And do get then on sale if possible.