It's not fair to call Piper and Mohler systematic theologians. They have not published a systematic theology. Mohler speaks to theological issues in an academic setting, and Piper is a pastor/theologian. Both are theologians to be sure, but you simply cannot compare them to those who have published full systematics.
Erickson's work is a goldmine and he interacts with....well, almost any theologian who has ever lived

It is a standard choice among many Baptist seminaries today because it strikes a mediating Calvinism and yet retains a full innerantist view (ironically, his doctoral mentor was Pannenberg). Back in the day, his larger work was green, and it was nicknamed the Green Monster!
Grudem is a wealth of information too. His strength is two-fold: One, he interacts significantly with biblical data. Not to say Erickson doesn't. Grudem just approaches it differently. Two, at the end of every section, Grudem gives you title and page numbers of various books from various segments to find their views. Wanna read what Charismatic theologians have written about spiritual gifts but don't know where to look? Grudem will point you there. What about the Methodist view of sanctification? His end of chapter bibliographies are worth the price of the book. He also includes major theological statements as well as Scripture memory passages and hymns that correspond with the doctrines. Some disagree with his Calvinism and his continualist views, but this should not dissuade you from owning this gem.
Garrett is worth reading. He seems to interact heavily, but at times leaves you wondering just what he actually thinks. For some reason, most moderate leaning Baptist schools I know utilize(d) this work.
Paul Enns has a work (Moody Handbook of Theology) that has a chapter on everything. However, it's a mile wide and an inch or two deep at best. If you want a 10 minute introducton to anything theological, get it. It's supplemental reading at best. It is heavily dispensational, fwiw.
A scant few used Theissen before the smaller Grudem and Erickson came along (there is even a condensation of the condensation of Grudem) but I wouldn't waste my time.
Daniel Akin recently edited
A Theology for The Church. I love Dr. Akin, but the problem with this book is various authors address the various viewpoints.
As for the dead guys, Boyce and Dagg are as good as you can want. Are they as large as Grudem/Erickson? Of course not. That's common sense. They are significant reads.
Non-Baptist theologians (living and dead) who are must reads: Thomas Oden. His 3 volume work on theology has now been condensed into one helpful volume called
Classic Christianity. Like Garrett and somewhat like Erickson, he interacts heavily with those who have gone before him. An evangelical Methodist, Arminians will likely welcome him
From a Dutch Reformed perspective, Bavinck's magesterial "Reformed Dogmatics" is classic. It has now been heavily edited down to one volume. It's a good starter, but the 4 volume is better (condensations usually are lacking, in my view). Charles Hodge's
Systematic Theology is free with the Online Bible package (so is Boyce) or you can get the print version for $19.99 from CBD. Watch out: Hodge thinks you know Latin (because you usually did back in his time). It was abridged into one volume but I don't recommend that one.
Warfield never produced a full systematic, but he is must-read.
And of course, there's Calvin's
Institutes. If you don't want to tackle the full work (and why not?), get the one volume edited by Lane and Osborne. You'll get a good taste. If you go for the full meal, don't worry a ton about the Battles edition vs. Beveredge.
Reymond's
New Systematic Theology is good. Turrentin's 3 vol Elenctic Theology is worth reading.