A321 pilot reported while taxiing to a parking spot a tug driver blocked them with a tug to prevent them from colliding with a nearby aircraft.

Narrative

Our flight was directed by Ramp to enter at Gate XX and proceed to Gate XY to taxi through into Gate XZ; West Holding Pad at ZZZ. It was nighttime; and visibility was very poor due to inadequate illumination (pitch black conditions).As we taxied northbound on taxiway 1; just a few yards past XY; my First Officer (FO) pointed out that we had missed our entry point. I corrected our course at a 20-degree angle toward the XY line; which we both visually confirmed. However; as we adjusted; I noticed another aircraft (a 737) ahead; which appeared to be too close for comfort. My FO assured me that we were indeed aligned with the XY taxi line; which had been assigned to us.Since it was very dark; we relied on visual confirmation. The XY line was particularly noticeable; as ZZZ does not have the same standard taxiway markings as other major airports. We proceeded cautiously; correcting toward the centerline. As we got closer; I remarked to my FO that the proximity to the other aircraft seemed unusually close. He reassured me that we were on the correct path and; at my request; opened his window to visually check that our wing was clear.We stopped as directed at the XZ spot. I made a PA announcement to the passengers; informing them that we were waiting for a gate. A few minutes later; a towing tug with a crew parked in front of our aircraft; blocking us. Through Ramp frequency; we were informed that our aircraft had been parked too close to the one at XA; and they requested that we shut down our engines so they could tow us. There was still a possibility of a collision during taxi.This was the closest I've come to colliding with another aircraft in my years as a rated pilot. The issue arose because Ramp was unaware that another aircraft was parked at XA. I owe deep gratitude to the ground crewman who proactively intervened and prevented what could have been hundreds of thousands of dollars in damage.Cause:Lack of communication; RAMP NOT KNOWING XA was occupied and lack of illumination in the area. I suggest Ramp has view of aircraft moving and parked. Also; although some improvements have been made at ZZZ; it is the worst hub with lines many times not existing.