Which was your favourite summons from the KH games? My favourite has to be Genie. His magic is very powerful and in KH2 he can cure you when ever you're in danger.
In KH1, I used Tinker Bell since she can come effective when fighting tough bosses that deal multiple blows like Chernabog. Plus, she can revive you one time, which is super uber.
In KH2, I used Genie since he can use various forms of power to deal critical hits. I barely use Summons in KH2 anyways since my Limits are spam-worthy.
I rarely used summons in KH. I thought they were pointless... The only one I ever used was Tinkerbell.
In KH2 the only time I used summons was in the Colosseum when you had to kill a whole bunch of monsters in a certain amount of time. I used genie cause he was the only good one. Final Form Genie was beat.