I think every Dragon Ball Z fan has at some point wished they could create their own character and plant them into the DBZ universe. Whether it be a forgotten android built by Dr. Gero or a Namekian with a grudge, everybody has wanted their dreamed-up character to trade blows with Goku. Dragon Ball Xenoverse allows this dream to be realized by providing the player with the tools to create their own character and insert them into series canon.
Time is under attack by a really shady figure named Demigra, who has been trapped in a crystal prison for billions of years. Aiding him are Towa and Mira, two incredibly dangerous individuals who go around corrupting events in history, changing the outcome to achieve their own twisted goals. Yes, Towa like Towa Wilcox, and just as pretty. Trunks, in order to protect the timeline, calls upon the eternal dragon Shenron with a wish for a warrior who is strong and can help him defend time. That's where you step in, the warrior summoned by Trunks himself, given the task of defending time alongside him.
You can be a Saiyan, a Human, a Namekian, Majin, or a member of Freiza's race. Apparently Freiza's species is so good it doesn't need a name. I call them "frost demons", but it doesn't matter what you call them 'cause they're all talk and not much substance. Saiyans have full favouritism, with special forms and unique skills that deal ridiculous damage. Every other race gets the short end of the stick, and it's also the end covered with poop.
You can equip your character with skills that you find, items you pick up and "Z-Souls" that have special abilities tied to them. All of these you can buy, find during missions or can be gifted to you via the in-game delivery system. By equipping the things that you find (the things that the everyday folks leave behind), you can create your ultimate fighter and really feel like part of the Dragon Ball universe. Uh, Universes. Man, this timeline is complicated. 12 universes, alternate timelines and dimensions AND Heaven and Hell? Toriyama, you're a maniac!
To defeat Demigra and his allies, you need to take on missions at the Time Nest. Whenever something goes awry in the timeline, you are inserted into the conflict to turn the events back to normal. Appreciating the game story therefore requires a decent understanding of Dragon Ball Z or Kai canon. To give an early example of the game's different scenarios, if Raditz was not defeated by Piccolo because he was somehow able to dodge the Special Beam Cannon, then the timeline would be altered and history would run another course. No doubt Raditz would kill Goku and Piccolo, lay waste to Earth, and then Freiza would sell the planet off. A grim alternate reality, which is avoided thanks to your character's efforts.
So think of the main story of this game as TimeBusters, I ain't afraid of no paradox! Nappa's a great ape? Call in the boys! But the real meat of the game comes from the side quests — or "Parallel Quests", thus named because they run in parallel to the real timeline. The PQs are a nice distraction because they'll sometimes stick you on the side of the bad guys or have you fight in battles that never happened in the show. In one PQ, Captain Ginyu (who has body switched with Goku) can become a Super Saiyan, it's crazy! (If you don't follow the show, that's probably all Chinese to you.) (And if you don't follow the show, why not?) (You're busy!? What kind of excuse is that! The episodes are like, 22 minutes each!) (Watch one a day, I bet you'll get so in to it you'll find the time to watch three or four!) (Don't give me that look!)
Supreme Kai of Time is cute, but I couldn't stomach that cooking every day...
The story is a solo affair, but Parallel Quests can be played online with friends. This is where Xenoverse has the most depth and enjoyment: Dragon Ball Z-obsessed buddies fighting together, crushing heroes and villains alike for that sweet loot. Sweet loot that is dropped randomly at weak percentage rates, missions that when fully completed still don't yield good rank scores, and outrageously unfair mission completion criteria that favours Saiyans. Finish the mission transformed for a better rank, which means the other races have to reach Level 95 to get their transformation. Hmmph. At least they fixed this in the sequel.
I certainly would have recommended Xenoverse while the sequel wasn't available, but now I'd be much more likely to recommend the later game. Most minor issues are fixed. And major issues. But the story of Xenoverse is far better than that of the sequel, as it doesn't depend on third rate characters and those fabricated for the movies.
In terms of compatibility — the PC port is very well-optimised and will work on all decent rigs. The game ran superbly on my six year old gaming PC and all newer machines, though Xbox One controllers are mapped incorrectly and can't be changed. Again, this is fixed in the sequel. Xbox 360 controllers are natively supported, though, so go buck wild on that one. The correct buttons display onscreen too, which can't be said about other PC ports of Japanese games. This runs fluently, none of those trappings from, say, a Tecmo Koei port.
As for consoles, I have played the Xbox One version through, and it runs smoothly on console with few major slowdowns, though not as smoothly as PC. Both the PC and Xbox One version have crashed on me at various points; the game isn't flawless in its construction but its regular autosave means no significant progress is lost. The servers for online play have been shoddy since the release of the second game but are still maintained. On launch the servers were trash, but now they're sturdy.
Between its online component and the story mode, Dragon Ball Z fans will have an excellent and enjoyable experience with Xenoverse. This cleverly punned 15th Dimps developed DBZ game (XV, geddit?) comes highly recommended, but a decent grasp of the show's main story events is a necessity.