Malkin is the best comparable, and Matthews was a better player and has a smaller cap hit percentage at equal term.
I get why people have skewed perception because of the insane McDavid contract and massive PP differences across eras, but Matthews' contract is not bad.
When Malkin signed his 5 yr post entry level deal at 15.34% of the cap we were in a period of significant growth in the CAP. Cap had increased by 12.8%/14.3% and 12.7% in each of last 3 years. It was reasonable to conclude that while 15.34% was a lot Cap would grow to fit the contract. He was also coming off a rookie season of 85 points and a second season of 106 points.
Mathews signs for 14.63% of the cap while we are coming off increases of 2.2%/2.7%/6%. Matthews was coming off a rookie year with 69 Pts and a 2nd year with 63 (yes I know 62 games) but Malkin had 106 in 82.
So yes they are comparable in that both were 5 yr contracts of ELC, Matthews cap% is marginally smaller 15.34 vs 14.63 but it was signed in a time of modest cap increases while Malkins was in a time of double digit % increases each year.
Not sure how one can conclude that Matthews was the better player. He had 132 points his first 2 years, Malkin had 191. Oh but yes Matthews is the best goal scorer since well the beginning of time. He had 74G his first 2 years. Malkin only had 80.
Malkin signed after a season in which he was second in the NHL it scoring. he was 18th his rookie season. Matthews was 22nd as a rookie and 61st his second year. Even if you do 2nd year on pts/game since we was injured you get 22nd again.
The contract may be comparable to Malkins in terms of term and cap hit % but the player is not.