Mike was such a huge part of why I was a BIG fan of Dream Theater. I mean I loved their music, which is a huge start, but back when I became a fan (2003), along with his drumming which I did and still do love he was so engaging with fans, was active with great special shows, setlist changes, and generally sent things out that caused heavy fan engagement and excitement. To me Mike is the single biggest factor in why Dream Theater was more than just a band I loved, and so he'll always have a special place for that.
After that it's hard to look past the duo that is Rudess/Petrucci. Sure, Moore and Sherinian have both played on a lot of material I've loved, but these two have been there the entire time I've been following just tearing things up.