Welcome to the forums!
So, you have asked the unanswerable question. Only you will know which is best for you. You do seem to know that there are many different "distributions" (distros) available as opposed to the very few Windows choices you have remaining. This is kind of like you telling us how far your commute to work or school is, how much traffic you encounter, what your personal driving patterns are, and whether there are any steep hills to consider.... and then asking what kind of car you should get? See what I mean?
Moving on, in order to try to help you. We know you have an older computer. The two main things to consider so that we may begin to offer you advice is whether you have a 32-bit or 64-bit CPU? And how much RAM you have? Don't be fooled by a Windows XP version that is 32-bit... many of them were. But they were still installed on 64-bit CPU's because that was a cheaper Windows version. But there really were some 32-bit CPU's too. You need to know this.
You do want to use 64-bit Linux if you can. Support for 32-bit anything is fading away, but if that is what you have you will still be able to do something better than XP, and you will still be able to get many years of service from your laptop. An older XP computer also means, for sure, that you have the old style BIOS, and not the more modern UEFI. This is a good thing for all new Linux users, in my opinion anyway.
The best way to find what is "best" for you is for you to download 2 or 3 different distros, burn them to DVD and try to boot them up. Even this brings up issues you may not have considered... such as, "Do you have a writable DVD drive to make these disks?" You could burn the DVD's on a different computer, but you'll need at least a DVD-ROM reading drive on the laptop. Or, do you know if your laptop will boot on a USB drive? Linux is most commonly installed with either USB or DVD, but I tend to favor DVD's because they're cheap and I don't mind throwing them away if they get corrupted during the burn process, or whatever.
So, the process is to download a (64-bit) Linux ISO file of the distro that you pick first... and then you have to use a special feature on your DVD burning software called, "Burn Image" to put that ISO onto the DVD. Don't just "copy" the ISO to the DVD, or else it will not boot. I'm not going to attempt to describe burning the ISO to a USB stick unless that is your only option. You'll have to let us know.
Here are some distros for you to consider. Google them and go to their websites to learn more about them and find their download links to get their ISO files. If you have 2 GB or more of RAM, you can run most anything... so try out Ubuntu, Linux Mint, Fedora, Debian, etc. If you have 1 GB of RAM or less, you will need to consider "light" distros that are lighter on hardware requirements. Some of these are Linux Lite, LXLE, Lubuntu, Simplicity Linux, Puppy Linux, etc. You can also find download links and other info on these, and even more distros at
http://distrowatch.com And if you want to see a bunch of screen shots of what some of the distros look like after they're installed, take a look at
http://www.linuxscreenshots.org
If you get a DVD burned and your laptop boots it up, most of the distros will run as a "live" system that you can check out a bit before you install it. This is a very nice way to try out different systems, but it is quite a bit slower than when installed to a hard drive. There is usually an icon on the desktop to install whatever it is that you're running. When your're ready, take the plunge and do it. I would suggest letting Linux install to the entire hard drive and letting it erase XP.
Oh, games... depends on what you want to do with that too. Some distros have a few games built in and there are others you can download. There are many Steam games made for Linux now, but you'll need the CPU/RAM to handle those. I'm not a gamer so I can't answer much to that.
Good luck!