1) The Astonishing: to me, this album is simply perfect. The melodies, the harmony, the arrangements, Rudess piano playing, Mangini's perfect orchestration throughout the whole album (all notes feel placed with all possible care and intention). If there's a DT album I know I can go back to and love it, is The Astonishing.
2a) A Dramatic Turn Of Events: technical, heavy, melodic, catchy, emotional... listening to it as a whole feels like an adventure. Lost Not Forgotten, Outcry and Breaking All Illusions have unmatched god tier instrumental passages. And Breaking All Illusions is their best song, imo.
2b) Dream Theater: like ADTOE, it is an adventure, but a more positive one. Similar to WDADU, it has lots of catchy moments and Rush-y vibe which I love. The Bigger Picture is easily one of their best songs to me (with very relatable lyrics). All of it is concise, tight and doesn't try to be anything it isn't. Can't decide between it and ADTOE, so they're tied for 2nd place.
3) When Dream And Day Unite: the lost Rush album, and damn it is really good. Despite the usual negative opinion on the album's production, it's my favourite DT album sonically. The songs are all catchy and amazing, and very focused (compared to most of their 2000s work, in my opinion), lyrics are some of the best, if you ask me. Dominici does a very good job too.