The answer to your question will depend in large part on how “Christian” a campus environment your desire.
Catholic schools in the US run the gamut from secular-in-all-but name (Georgetown) to solidly “Catholic” (Notre Dame, Holy Cross) to forthrightly pious (Franciscan University of Steubenville, Thomas Aquinas College [a small, Great-Books oriented LAC located in rural SoCal]).
I would say that Notre Dame (a major research university) and Holy Cross (a fine liberal arts college known for strength in the humanities) manage to be academically strong while preserving a distinctive Catholic identity that still remains open to non-Catholic points of view.
With Protestant schools, things are a bit less clear cut. Many of the oldest and most prestigious American universities and colleges have roots in the Protestant tradition. Some of these jettisoned those religious connections long ago (e.g., Harvard, Yale, Dartmouth), while for others the break has been more recent (Duke, Emory, Wake Forest). A few universities (e.g., SMU) continue to have a nominal Protestant affiliation, but one that doesn’t really impact the ebb and flow of campus life.
Of the schools that are more overtly Christian/Protestant in orientation, some tends towards a generic social and cultural conservatism (e.g., Pepperdine), while a few attempt to offer a genuinely Christian atmosphere as an alternative to the de facto secularism of mainstream culture. The best-known of this last group is probably Wheaton College (outside of Chicago), which has long enjoyed a reputation as the intellectual flagship of evangelical Christianity in the US; others in this group would include Biola (near LA), Westmont College (also in SoCal), Gordon College (in Massachusetts), and Calvin College (in Michigan).
Were I to choose from the above schools based on your stated criteria, I would probably opt for Notre Dame (Catholic university), Holy Cross (Catholic LAC), or Wheaton (Protestant LAC), all of which are academically strong and have good track records of sending students on to graduate study in a range of fields.
There are, of course, many other options. To get a general idea of what’s on offer, you might check the Princeton Review’s list of colleges with “Most Religious Students” and look at the Niche rankings of “Best Christian Colleges in America.” You should also be aware that there are many committed Christian students at even the most secular of mainstream educational institutions. Sometimes, these students manage to build a powerful sense of community precisely because theirs is a marginalized voice on campus. In short, don’t dismiss non-religious schools from your search at the outset. Take the time to research the nature of the faith communities present on each campus.