As someone who played the first X-com (the one from the 90s) , allow me to make some observations on this game. You may or may not agree with them , but thank you for reading. I'll place this game in a side-by-side comparison with the 90s classic:
1) The weakest part of this remake is that no. of maps are LIMITED. It's quite immersion breaking when you realize you've been through the same areas over and over again.
The original used procedurally generated maps , which basically means randomly generated maps. So , it makes each battle quite unpredictable as opposed to the fixed maps where you know the best places to position your troops.
2) In the remake , the aliens always spawn at set positions on the map. Not only this, but they NEVER START MOVING AS SOON AS THE GAME STARTS. They only react when the player "triggers" them.
In the original, the aliens would spawn at random positions , and they start moving as soon as their turn starts. This made the battle more challenging and unpredictable , because in the Remake you ALWAYS know where they'll be if you've played through the map at one point and you KNOW they WON'T MOVE from that spot until you've triggered them.
3) In the remake , you're only in command of a single base. Besides this , in UFO interceptions you can only send ONE interceptor after it. Also, you can only do ONE mission at a time.
In the original, you could have several bases all over the world (cost would increase with each new base being developed). This allowed you to create special bases for Research , Production , Interception. Upside of this is that you can quickly speed up research and your engineers can produce items faster. Also , with bases created especially for UFO Interception (strategically positioned between two continents), your interceptors can get to the UFOs before they land. Downside? Well , more bases means more micromanagement , but again this depends on you - how many bases do you need to defeat the aliens?
Also , you can send out multiple interceptors after the same UFO (absolutely necessary when you want to down that big bad guy in the sky without him landing and spawning terror missions). The best part is that you can send out squads on multiple missions at the same time. Unlike the remake, you are NOT forced to choose between saving regions.
4) In the remake, you cannot deploy any vehicles at all. By that I mean tanks , hovertanks e.t.c .
In the original, you could deploy tanks and other vehicles researched from alien wreckage. They were very useful for scouting ahead , thus saving your soldiers from surprise attacks from the aliens.
5) Now here comes the biggest difference between this game and the original - soldier specializations. This is something the developers really messed up imo , and allow me to explain this further.
In the remake, you get Soldiers based on their specializations. For example, a heavy weapons guy cannot use sniper rifles and vice versa. Also , you get these soldiers randomly , so you cannot fill that empty sniper spot until that particular rookie gets RANDOMLY promoted to Sniper. Also , each soldier is given a limited no. of grenades / rockets. It's so limited you wonder where all the space in that suit is gone, and the grenades don't do much damage either.
Also in the remake, you can only take a squad of six into battle. Now , losing even one of them early in the battle can make the whole affair unwinnable as you get swarmed by aliens. My biggest gripe here is that YOU CANNOT PICK UP STUFF FROM FALLEN SOLDIERS/ENEMIES ON THE BATTLEFIELD. See that medkit on your dead soldier? Yeah , it's useless until the end of the battle , gg.
In the classic , any soldier can use any weapon BUT there's a catch. Each soldier has stats related to their expertise in weapons. Some soldiers do naturally come as good sharpshooters ,so they're best with a sniper rifle - BUT you can give them a heavy weapon. The only thing is they'll be far less accurate at making their shots compared to a specialist , but given time they CAN improve on a gun they're not used to.
Also, you can stash more grenades/rockets on a soldier and they do decent damage as well. With regards to squad size, you have a max no. of slots depending on the vehicle you transported them in. So , taking a tank along might occupy the slots for 4 soldiers. If I remember right, you can field 26 soldiers on the battlefield depending on the vehicle. You can also pick up weapons from fallen comrades and even ALIENS.
Downside is that too many soldiers means the battles can get prolonged. Then again, the aliens sometimes also come in large squads (depending on the type of UFO that dropped them there) , so you will need those extra troops to match them. Having more soldiers also means that the loss of a single man doesn't necessarily turn the overall tide of the battle unlike the remake.
SUMMARY
To summarize , while Xcom : EU does seem inferior to the original X-Com in many ways , keep in mind that it's been heavily dumbed down to appeal to a more mainstream audience. If like me you played the original X-Com , you will not like the remake. My advice to such players is to treat Xcom : EU as a different one from the remake and play it on it's own merit.