So I am thinking of bringing this homebrew house rule for counterspell to my game (I got the idea from Davvy Chappy). The reason for doing this is that I found myself creating encounters based around that spell. It burns through reactions and it just turns into a game of who can cancel out the spell the most (enemy casts fireball, counterspell, well he also casts counterspell, well now the warlock is counterspelling his counterspell, etc).

Here is the idea:

When counterspell is cast each character rolls a d20 and add their spell casting modifier plus a modifier equal to the difference in spell level (ex. if the counterspell is lv 3 and the spell is lv 1 the caster gets a +2 on the account that the counterspell is a stronger spell. But if the counterspell is lv 3 and the spell is lv 5 you get a -2 because you're trying to beat a stronger spell). If the caster of counterspell wins, their spell goes off and the opposing mage's spell fails. If the target wins they manage to harness their focus and push the offending mage's magic (counterspell) away from their spell. 

I was also thinking that this could add some interesting flavor to combat when it comes to spellcasters. When I showed this to my group the Wizard, of course, had a problem with this because he felt that I was taking something away from his character. His argument was that he doesn't get any other reaction and that counterspell is one of his only defenses. He also made the argument that people build their characters a certain way and taking something that is an instant success, like counterspell, and making it more a chance of the rolls, takes away something the character worked hard for. I tried to explain that the higher level you are or cast the spell the more modifiers you get, therefore allowing more of a chance for success-but he was like there's still a chance of a 3rd level wizard defeating an 8th level wizard and that it wasn't fair. 

What are your thoughts?

i think the rule might work, but i would suggest doing it only when the opponent uses a higher level spell, also when you implement the house rule allow them to switch out counterspell for a different spell if they want

If you want to do something like that, I would suggest one change:

Rather than having it be a contested roll, treat it as a skill challenge. The one casting counterspell rolls a D20 and adds or subtracts the difference in spell level and pits that result against the initial spellcaster's spell DC. If the spell DC is met, the initial spell is countered.

It can be assumed that the higher spell DC is the result of a more powerful spellcaster, so a simple bad roll by the higher level spellcaster causing him to be counterspelled disappears and is no longer "unfair".

Quote from Warranto >>

If you want to do something like that, I would suggest one change:

Rather than having it be a contested roll, treat it as a skill challenge. The one casting counterspell rolls a D20 and adds or subtracts the difference in spell level and pits that result against the initial spellcaster's spell DC. If the spell DC is met, the initial spell is countered.

It can be assumed that the higher spell DC is the result of a more powerful spellcaster, so a simple bad roll by the higher level spellcaster causing him to be counterspelled disappears and is no longer "unfair".

 I feel that if I was to do that I might as well not change it at all or just take away that instant fail and have a roll every time. Part of the contested is to add to the roleplay and add a sense of excitement and uncertainty. Maybe the players are facing a high level mage and his hubris causes him to over confident and the lowly mage counterspells his magic, that and having to do the die roll just adds to the tension.