Well, think about it - early FF's didn't offer anything unique/spectacular - even with VI they were rubbish in battle, gave you no incentive to use them other then for learning spells off.
VII's, no incentive to really use them unless it was a Bahamut. IX, same old summon this, attack the enemy etc. X - so you could teach them abilities. In the end, wasn't it better just to focus on getting on their overdrive and using standard attacks? XII's - pretty much like the earlier FF's - weren't really that useful for anything.
VIII's, actually made summons worthwhile, and you actually could use them for something worthwhile outside of battle, like learning valuable strength and magic boosts, increasing a summons attack/HP, learning some skills, and you could also delete pointless skills if possible. Their cards had value too - you could also convert them into special items. They also provided back up in battle - say you were on low HP, and you summoned a monster - that monster would pretty much take a hit for you, giving you time to either make a comeback/finish a fight or heal yourself.
Other things make this fun too - you could fight various summons by going to secret places - not unique I know, but, in order to fight and obtain Bahamut, you had to answer questions in a particular order, to fight and obtain Odin you had to find him in a race against time, and to get Tonberry King, you had to fight Tonberries 20 times! To get Doomtrain, you had to collect specific items. I thought it was pretty cool too when you had to draw some summons too!
Sure, you can say that other games required you to hunt for optional summons, but it wasn't exactly challenging. In VII, you had to find the materia. Whooptydo. X - you had to go to cloisters/faythy place and get Yuna to obtain them. Challenging.
XII could match VIII in terms of challenging ways to find Espers and fight them. Like completing a specific sidequest to reach Zalera and killing/defeating it in a short amount of time seeing as the match had a time limit. And Cuchulainn - the whole area had a sap effect on it. The most powerful esper Zodiark - you could only get to by capturing at least 10 other espers, speaking to Geomancer Yugelu in Jahara to get him to unlock a certain area in the Henne Mines for you.
So in other words pretty much..VIII summons > every other FF's summons.
VII's, no incentive to really use them unless it was a Bahamut. IX, same old summon this, attack the enemy etc. X - so you could teach them abilities. In the end, wasn't it better just to focus on getting on their overdrive and using standard attacks? XII's - pretty much like the earlier FF's - weren't really that useful for anything.
VIII's, actually made summons worthwhile, and you actually could use them for something worthwhile outside of battle, like learning valuable strength and magic boosts, increasing a summons attack/HP, learning some skills, and you could also delete pointless skills if possible. Their cards had value too - you could also convert them into special items. They also provided back up in battle - say you were on low HP, and you summoned a monster - that monster would pretty much take a hit for you, giving you time to either make a comeback/finish a fight or heal yourself.
Other things make this fun too - you could fight various summons by going to secret places - not unique I know, but, in order to fight and obtain Bahamut, you had to answer questions in a particular order, to fight and obtain Odin you had to find him in a race against time, and to get Tonberry King, you had to fight Tonberries 20 times! To get Doomtrain, you had to collect specific items. I thought it was pretty cool too when you had to draw some summons too!
Sure, you can say that other games required you to hunt for optional summons, but it wasn't exactly challenging. In VII, you had to find the materia. Whooptydo. X - you had to go to cloisters/faythy place and get Yuna to obtain them. Challenging.
XII could match VIII in terms of challenging ways to find Espers and fight them. Like completing a specific sidequest to reach Zalera and killing/defeating it in a short amount of time seeing as the match had a time limit. And Cuchulainn - the whole area had a sap effect on it. The most powerful esper Zodiark - you could only get to by capturing at least 10 other espers, speaking to Geomancer Yugelu in Jahara to get him to unlock a certain area in the Henne Mines for you.
So in other words pretty much..VIII summons > every other FF's summons.