Are they any good??
I have never played an XCOM\UFO game but the announcement of a reboot received such "praise" from fans that it inspired an interest in me to check it out.
Also, I should mention, I tried, for five minutes, the UFO: Enemy Unknown and I have no idea what to do or how to play that game. I think that's because in DOS time the tutorials and story were on the manual...

Be careful, the UFO series we have on GOG is *not* the X-COM series (which includes UFO: Enemy Unknown). It's an entirely different series that took some inspiration from X-COM.

Yeah I know.
But how are they compared to the UFO: Enemy Unknown and are they generally good games??

UFO : Enemy Unknown, and the X-Com games in general, are what is called "Squad-Level Tactics" games.

*On the map-screen, you pick a location for your base, and then build it up, as funds allow.
*You hire staff to form your squad(s), and equipment for them to use.
*You hire scientists and workers to research and develop new items (or captured alien tech) from missions.
*You purchase fighters, to shoot the UFOs down, and transports to get your squads to missions.

In a mission, you direct your squad to Search&Destroy alien attackers of varying strengths and capabilities, and loot them for tech. Saving civilians is a bonus, but not necessary.

Rinse and repeat until you run out of funds, aliens conquer the world (forcing governments to hide them, and influencing them to stop funding you), or you somehow manage to drive them away completely.

Once you get going, you can build more bases in strategic locations to intercept aliens quicker, but your first should always be somewhere in UK/Europe or North America.

Basically, I treat UFO:EU as a game of the old Gerry Anderson live-action TV series of "UFO", and name my bases and craft and personnel after that :P

They can be okay semi-realtime based strategy games if you're into tactical battles and such.
Best way to find out about whether it's something for you might be something like a Demo. The Demo should work on x64, I know the full game does on my Vista x64, though it was a pain getting Starforce to work with a 64-bit system.